Appropriate management of thyroid dysfunction in pregnancy is challenging in both its primary, secondary and tertiary forms of the disease. Primary hypothyroidism is by far most prevalent globally. Main causes are insufficiency of iodide supplementation in developing countries and autoimmunity in developed countries. However, after a very successful global implementation by World Health Organisation over decades accompanied by specific recommendations for management of the iodide supplementation during pregnancy, recent studies found that women both in USA and EU are again mild to moderately iodide deficient during pregnancy or going through assisted fertility treatment. This poses a disturbing risk in relation to foetal neurological and brain development. The diagnosis and treatment monitoring of the thyroid function during pregnancy are very challenged due to the extensive physiological as well as pathophysiological adaptations of the thyroid axis hormones to encompass a sufficient foetal supply. This is distorting the hormone measurements, since the normal limits are exceeded, and current biochemical methods are not calibrated for the adapted concentrations. Even though clinical guidelines exist there are still gaps in the evidence-based recommendations to guide clinicians to thyroid function management during pregnancy. Debut of hypothyroidism during pregnancy requires immediate diagnosis as it can lead to poor foetal outcome with intrauterine growth restriction and foetal demise on top of the risk for the neurocognition. Hypothyroidism in stable replacement treatment needs careful monitoring during pregnancy to adapt to the physiological changes in the requirement of the thyroid hormone thyroxine, and combination therapy with triiodothyronine is contraindicated. The frequent use of assisted reproduction technology (ART) with controlled ovarian hyperstimulation in these patient groups having disease induced low fertility has created an unrecognised risk of under-replacement due to accelerated oestrogen stimulation with increased risk of severe complications for both the woman and foetus. Longitudinal studies of the thyroid function bridging pre-ART, through ART to pregnancy and postpartum in different clinical settings are recommended. The area needs consensus recommendations between gynaecologists and endocrinologists in specialised centres to alleviate such increased gestational risk. There is a strong need of more research on improvement of thyroid hormone replacement, and biomarkers for treatment optimisation in this field of non-communicable diseases, which suffers from both limited attention from the health authorities and poor funding.

A significant number of patients with primary hypothyroidism report persistent symptoms and decreased quality of life (QoL) despite biochemically adequate levothyroxine replacement. Individual variations in thyroxine conversion, autoimmune inflammation, and psychological factors have all been implicated as a potential cause.

In this cross-sectional study we have examined the association of numerous demographic, disease-specific, and laboratory parameters as well as three patient reported outcome measures with thyroid-dependent QoL as measured by the Underactive Thyroid-Dependent Quality of Life Questionnaire. Patients were stringently selected to minimize the confounding effect of comorbidities or inadequate hormone replacement. We used validated questionnaires to assess somatosensory amplification, depression, and symptom number. Determinants of QoL were evaluated using uni- and multivariable linear modeling, and mediation analysis.

Our final sample consisted of 157 patients. 70.7% had Hashimoto's, whereas 29.3% had iatrogenic hypothyroidism. Mean age was 49.5 ± 14.5 years, disease duration: 11.2 ± 8.2 years, thyroxine dose: 1.2 ug/kg bodyweight, TSH: 1.8 ± 0.9 mIU/L. Thyroid-specific biomarkers including TSH, FT3, FT4, rT3, SPINA-GD, anti-TPO, and SHBG had no association with thyroid-dependent QoL. Somatosensory amplification was a strong predictor of the presence and perceived bother of the most common hypothyroidism-associated symptoms. In our final multivariable model (r2 = 0.31) the factors associated with thyroid-dependent QoL were somatosensory amplification (p = 0.002), BMI (p = 0.021), and depression (p < 0.001).

These results suggest that psychological factors, particularly somatosensory amplification, might play a major role in influencing QoL in hypothyroid individuals on adequate levothyroxine replacement. Our findings do not corroborate a significant role for autoimmune inflammation or tissue-level hypothyroidism.

Background: Thyroid dysfunction is common in older adults and poses diagnostic and management challenges for clinicians. In this narrative review, we present published data focusing on special considerations in the diagnosis and management of hypothyroidism and hyperthyroidism in older adults. Methods: A comprehensive literature search of the PubMed and Ovid MEDLINE databases was conducted from January 2000 to December 2024 to identify pertinent articles in English for this narrative review. Results: Due to significant cardiovascular risk if untreated, both overt hypothyroidism and hyperthyroidism should be treated in older adults. Findings from observational studies do not support treating older adults with subclinical hypothyroidism with a thyrotropin (TSH) <7 mIU/L. However, observational data have demonstrated an increased risk of cardiovascular mortality and stroke in older adults with subclinical hypothyroidism with TSH 7.0-9.9 mIU/L and of coronary heart disease, cardiovascular mortality, and heart failure in those with TSH ≥10 mIU/L, suggesting levothyroxine treatment in these individuals should be considered. Data from clinical trials failed to show improvement with levothyroxine in hypothyroidism symptoms or fatigue in older adults with subclinical hypothyroidism compared with placebo. Over- and under-replacement with thyroid hormone is common and should be avoided, as population-based studies have shown associations with adverse cardiovascular and skeletal events. Subclinical hyperthyroidism with a TSH <0.1 mIU/L should be treated in older individuals as it has been associated with increased cardiovascular risk and bone density loss based on observational data. Randomized controlled trials have shown that long-term low-dose methimazole is a viable alternative to radioactive iodine in older adults with hyperthyroidism. Conclusions: A personalized approach should be undertaken in the diagnosis and management of thyroid dysfunction in older adults. Multiple factors should be considered, including physiological age-related changes in thyroid function, comorbidities, and polypharmacy. Care should be taken to maintain euthyroidism in order to avoid adverse events.

Levothyroxine (LT4) is commonly prescribed, but there is evidence strongly suggesting that a significant proportion of these patients are on treatment without solid evidence of hypothyroidism. Small trials on treatment discontinuation, did not detect any predictors of success. Therefore, we conducted this study in an attempt to identify predicting factors for successful LT4 withdrawal.

In 802 consecutive patients (83% females, mean age 48 ± 16 years) on LT4 treatment for 8.8 ± 7.3 years without a solid diagnosis of hypothyroidism, therapy was abruptly discontinued. A total of 387 persons were followed up for up to 4 months (group A) and 415 individuals who were euthyroid at 4 months post LT4 discontinuation, were followed up for up to 60 months (group B). Recurrent hypothyroidism was defined if thyrotropin (TSH) level exceeded 4.5mIU/L.

Among the entire cohort, 182 patients (23%) became hypothyroid, 40% of group A and 7% of group B (p < 0.001). The Τhyroid treatment Discrimination Index (T4RxDI), the product of TSH levels multiplied by the daily LT4 dose divided by BMI, was calculated. In group A, successful LT4 withdrawal was strongly indicated by a T4RxDI value < 2.78 (72% sensitivity, 66% specificity), while in group B, the corresponding value was 3.75 (100% sensitivity, 48% specificity).

Our findings reveal considerable overuse of LT4 and propose a T4RxDI product of < 3 as a valuable predictive factor of recurrent hypothyroidism, justifying a treatment discontinuation trial. If hypothyroidism does not resume within 4 months, the risk of developing long-term hypothyroidism is likely to be minimal.

For many years, pharmaceutical expenditure has been the second largest cost item for statutory health insurance funds (SHI) in Germany after hospital costs. Since prescriptions and expenditure on medicines play such a major role in the German healthcare system, the question arises as to what causes changes in prescriptions. To answer this question, the prescribing trends for the top 10 drugs in 2022 were analyzed over a period of 38 years, from 1985 to 2022. The prescribed defined daily doses (DDD) and the costs per defined daily dose for the 10 medicines were taken from the Arzneiverordnungsreport (AVR) from 1986 to 2023, and the changes in prescribing behavior and their causes were analyzed. The ten most important medicines in 2022, accounting for over 41% of all prescribed daily doses, were ramipril, candesartan, pantoprazole, amlodipine, atorvastatin, levothyroxine, torasemide, simvastatin, bisoprolol, and metoprolol. There are many different reasons for an increase in prescriptions, such as the introduction of generics, a positive study, or a price reduction. Further reasons for an increase in prescriptions are an extension of the indication or the recall of a competing medicine. A change in guidelines or the increasing treatment of laboratory values without clinical symptoms can also lead to an increase in prescriptions. There are also many different reasons for a drop in prescriptions, such as the generic launch of a competitor medicine or a positive study for a competitor medicine. Other reasons for a drop in prescriptions are a negative study or a discussion about the use of a drug. Sometimes, the reasons for prescription changes are also irrational. Overall, this is the most comprehensive long-term analysis of drug prescriptions in Germany. Our data is helpful for predicting drug prescriptions and for preventing future drug shortages not only in Germany but also worldwide.

Thyroid hormone is one of the most commonly prescribed medications in the United States. Misuse of and overtreatment with thyroid hormone is common in older adults and can lead to cardiovascular and skeletal adverse events. Even though deprescribing can reduce inappropriate care, no studies have yet explored specific barriers and facilitators to guide thyroid hormone deprescribing in older adults (defined as discontinuation of thyroid hormone when initiated without an appropriate indication or dose reduction in those overtreated).

We conducted semi-structured interviews with 19 endocrinologists, geriatricians, and primary care physicians who prescribe thyroid hormone. Interviews were completed between July 2020 and December 2021 via two-way video conferencing. We used both an inductive and deductive content analysis guided by the Theoretical Domains Framework to evaluate transcribed and coded participant responses. Thematic analysis characterized themes related to barriers and facilitators to thyroid hormone deprescribing practices in older adults.

The most commonly reported barriers to thyroid hormone deprescribing were related to patient-level factors, followed by physician- and system-level factors. Patient factors included patients' perceived need for thyroid hormone use and patient anxiety/concerns about potential side effects related to thyroid hormone dose reduction, patient lack of knowledge, and misinformation regarding deprescribing. Physician- and system-level barriers included clinic visit time constraints, physician inertia, physician lack of knowledge about deprescribing, perceived lack of sufficient patient follow-up, and electronic health record limitations. The most prominent physician-reported facilitators to thyroid hormone deprescribing were effective physician-to-patient communication, and positive physician-patient relationship, including patients' trust in their treating physician.

Barriers and facilitators to thyroid hormone deprescribing in older adults were reported at multiple levels including patient-, physician-, and system-level factors. Interventions to improve thyroid hormone deprescribing in older adults should aim to improve patient education and expectations, increase multidisciplinary physician awareness, and overcome physician inertia.

Previous studies showed sex differences in the prevalences of both major depressive disorder (MDD) and subclinical hypothyroidism (SCH). This study aimed to further compare the prevalence and correlates of moderate-to-severe SCH between male and female Chinese MDD patients.

A total of 1706 first-episode drug naïve Chinese patients with MDD were recruited. Depressive symptoms were assessed by the 17-item Hamilton Depression Rating Scale, psychotic symptoms by the Positive and Negative Syndrome Scale and anxiety symptoms by the Hamilton Anxiety Rating Scale. Serum thyroid stimulating hormone (TSH), free triiodothyronine (fT3) and free thyroxine (fT4) concentrations were measured by chemiluminescence immunoassay. Moderate-to-severe SCH was defined as serum TSH > 8 mIU/L with normal fT4.

The prevalence of moderate-to-severe SCH was 10.4% in male patients and 15.1% in female patients (χ2 = 7.22, p < 0.01). In female patients, binary logistic regression showed that systolic blood pressure (SBP), suicide attempts and psychotic symptoms (all p < 0.001) were associated with moderate-to-severe SCH. In male patients, SBP and psychotic symptoms were associated with moderate-to-severe SCH (both p < 0.001), while suicide attempts and severe anxiety were not (p > 0.05).

Our findings reveal a higher prevalence rate of moderate-to-severe SCH in female untreated first-episode MDD patients compared with males. Moreover, there is a positive association between suicide attempts and moderate-to-severe SCH only in female MDD patients.

Excess thyroid hormone is a well-documented risk factor for the development of atrial fibrillation (AF). The purpose of the study is to assess incidence of AF in patients taking levothyroxine for hypothyroidism and correlate it with biochemical thyroid function.

This was a retrospective cohort study of patients aged 18 years and older who were treated with levothyroxine. Exclusion criteria were pre-existing diagnosis of AF and use of amiodarone in the prior year. Patients were followed 2012 through 2019 and stratified into 4 groups based on mean thyroid-stimulating hormone (TSH) value or mean fT4 value in 2012. Primary outcome was incidence of AF. Rates of AF between groups were assessed via Poisson regression with control of underlying confounders.

Of 21,035 patients, 1091 (5.2%) developed AF during follow-up. Thyroid-stimulating hormone at baseline was not significantly associated with incident AF. Higher fT4 levels at baseline were associated with increased AF risk in age- and sex-adjusted analyses (hazard ratio 1.22; 95% CI, 1.03-1.44) for the highest quartile versus the lowest quartile of fT4.

In hypothyroid patients treated with levothyroxine, higher circulating fT4 levels are associated with increased risk of incident AF. There is no association of serum TSH with risk of AF. In patients at risk for AF, consideration should be given to avoiding fT4 levels in the highest quartile.

A growing body of evidence indicates a strong association between exogenous thyroid hormone (ETH) and brain health. Establishing the potential relationship between ETH therapy and dementia symptoms is crucial for patients with thyroid disorders.

In this study, we investigate the potential association between ETH therapy and dementia symptoms by exploring the Food and Drug Administration Adverse Event Reporting System (FAERS) database.

Disproportionality analysis (DPA) was conducted using postmarketing data from the FAERS repository (Q1 2004 to Q4 2023). Cases of dementia symptoms associated with ETH therapy were identified and analyzed through DPA using reporting odds ratios and information component methods. Dose and time-to-onset analyses were performed to assess the association between ETH therapy and dementia symptoms.

A total of 9889 cases of ETH-associated symptoms were identified in the FAERS database. Dementia accounted for a consistent proportion of adverse drug reactions each year (3.4%-6.3%). The DPA indicated an association between ETH therapy and dementia symptoms, which remained significant even across sex, age, and indications. The median time-to-onset of dementia symptoms was 7.5 days, and the median treatment time was 40.5 days. No significant dose-response relationship was observed.

This study provides evidence for a link between ETH therapy and dementia. Clinicians are therefore advised to exercise vigilance, conduct comprehensive monitoring, and consider individualized dosing to mitigate potential reactions to ETH drug administration.

Persistent symptoms are common in the general population and even more so in people with hypothyroidism. When symptoms are unexplained and brought to medical attention, they can be referred to as medically not yet explained symptoms (MNYES), a term preferred to other descriptors by patients, care-givers and experts. MNYES might be neglected by endocrinologists or misattributed to hypothyroidism. Awareness of MNYES could open up more effective and less harmful interventions for patients who present to endocrinologists with unexplained symptoms than costly over-investigations and over-treatment with thyroid hormones (such as levothyroxine and liothyronine). The role of the endocrinologist is to recognize and acknowledge that MNYES could be underlying a patient's presentation, to communicate effectively with the patient and others involved in the patient's care, to apply a 'two-track approach' in management by paying equal attention to physical and psychosocial contributors, and to collaborate with other relevant health professionals. Categorization of patients into levels of risk for symptom deterioration helps in selecting suitable therapies. Effective management of MNYES demands time, training, expertise and resources.

Background: Thyroid-stimulating hormone (TSH) and subsequent free thyroxine (FT4) concentrations outside the reference interval (RI) are used to diagnose thyroid diseases. Most laboratories do not provide age-specific RIs for TSH and FT4 beyond childhood, although TSH concentrations vary with age. Therefore, we aimed to establish TSH and FT4 age-specific RIs throughout life and aimed to determine whether using these RIs would result in reclassification of thyroid disease diagnoses in adults. Methods: This multicenter retrospective cross-sectional study used big data to determine indirect RIs for TSH and FT4. These RIs were determined by TMC and refineR-analysis, respectively, using four different immunoassay platforms (Roche, Abbott, Siemens, and Beckman Coulter). Retrospective data (2008-2022) from 13 Dutch laboratories for general practitioners and local hospitals were used. RIs were evaluated per manufacturer. Age groups were established from 2 to 20 years by 2-year categories and decade categories between 20 and 100 years. Results: We included totally 7.6 million TSH and 2.2 million FT4 requests. TSH upper reference limits (URLs) and FT4 lower reference limits were higher in early childhood and decreased toward adulthood. In adulthood, TSH URLs increased from 60 years in men, and from 50 years in women, while FT4 URLs increased from 70 years onward. Using adult age-specific RIs resulted in a decrease in diagnoses of subclinical and overt hypothyroidism in women above 50 and men above 60 years in our Roche dataset. Conclusion: This study stressed the known importance of using age-specific RIs for TSH and FT4 in children. This study also showed the clinical relevance of using age-specific RIs for TSH in adulthood to reduce diagnoses of subclinical hypothyroidism in older persons. Therefore, implementation of adult TSH age-specific RIs should be strongly considered. Data are less uniform regarding FT4 age-specific RIs and more research should be performed before implementing these in clinical practice.

Levothyroxine (LT4) is recommended to be ingested in a fasting state, 30-60 minutes before breakfast to avoid interactions with food and drugs. In clinical practice, we noticed that this instruction may be inconvenient for patients. Therefore, we aimed to evaluate patient experiences and preferences concerning the recommended fasting administration of LT4.

Patients using LT4 were invited to complete a questionnaire. Regression analyses were performed to identify patient characteristics associated with taking LT4 close to or together with food and/or interfering drugs, feeling burdened with postponing breakfast, and preferring nonfasting LT4 ingestion.

Of 463 invited patients, 410 completed the questionnaire (88.6%). Of these, 76.8% was female and median age was 57 years (interquartile range: 43-67). Nearly all patients (97.3%) reported to have received instruction on fasting LT4 ingestion, but only 30% adhered to this. Nonfasting LT4 intake was associated with use of co-medication (odds ratio [OR], 2.82; 95% CI, 1.77-4.47), treatment duration >1 year (OR, 1.76; 95% CI, 1.02-3.04), and male sex (OR, 1.67; 95% CI, 1.03-2.70). Approximately half of the patients reported being burdened with postponing breakfast and the majority (60.5%) expressed their preference for nonfasting LT4 ingestion. Interestingly, 25% omitted breakfast and 13.4% forgot their medication because of the fasting requirement. Furthermore, the majority (68.2%) of patients that used interfering drugs stated not to be instructed to separate these drugs from LT4.

This study highlights the burden associated with fasting LT4 ingestion, leading to nonadherence, irregular LT4 intake, and omitting breakfast. Given the clear preferences towards nonfasting LT4 ingestion, further research into alternative nonfasting administration methods is warranted.

Hypothyroidism, the deficiency of thyroid hormone, is a common condition worldwide. It affects almost all body systems and has a wide variety of clinical presentations from being asymptomatic to, in rare cases, life threatening. The classic symptoms of hypothyroidism include fatigue, lethargy, weight gain, and cold intolerance; however, these symptoms are non-specific and the diagnosis is typically made on biochemical grounds through serum thyroid function tests. The most common cause of hypothyroidism is chronic autoimmune thyroiditis (Hashimoto's thyroiditis), although other causes, including drugs (such as amiodarone, lithium, and immune checkpoint inhibitors), radioactive-iodine treatment, and thyroid surgery, are frequent. Historically, severe iodine deficiency was the most common cause. Reference ranges for thyroid function tests are based on fixed percentiles of the population distribution, but there is increasing awareness of the need for more individualised reference intervals based on key factors such as age, sex, and special circumstances such as pregnancy. Levothyroxine monotherapy is the standard treatment for hypothyroidism; it is safe and inexpensive, restores thyroid function tests to within the reference range, and improves symptoms in the majority of patients. However, 10% of patients have persistent symptoms of ill health despite normalisation of thyroid function tests biochemically and a substantial proportion of patients on levothyroxine have thyroid-stimulating hormone concentrations outside the reference range. Ongoing symptoms despite levothyroxine treatment has led to some patients using liothyronine or desiccated thyroid extract. Taken together, these factors have led to intense debate around the treatment thresholds and treatment strategies for hypothyroidism. In this Seminar, we review the epidemiology, genetic determinants, causes, and presentation of hypothyroidism; highlight key considerations and controversies in its diagnosis and management; and provide future directions for research.

To analyze the evolving epidemiologic trends in thyroid disease, focusing on risk factors, underlying drivers of these changes, and their implications on clinical practice and research priorities.

Thyroid disease remains one of the most prevalent groups of disorders globally, and the shift in its frequency and distribution is multifactorial. The prevalence of hypothyroidism increases with age, although normal thyrotropin ranges appear to be age-dependent, raising concern for potentially inappropriate levothyroxine use. Hyperthyroidism and Graves' disease continue to be predominant in reproductive-age women but exhibit a milder phenotype at diagnosis. Thyroid nodules are increasingly found in asymptomatic patients, likely from more widespread use of neck and chest imaging. Thyroid cancer incidence has risen exponentially over the years, mostly driven by overdiagnosis of low-risk tumors; however, a small rise in incidence of higher risk tumors has been noted. Obesity appears to be a risk factor for thyroid cancer occurrence and more aggressive forms of the disease.

Understanding epidemiologic trends in thyroid disease is crucial for guiding clinical practice and research efforts, aiming to optimize patient outcomes while preventing unnecessary and potentially harmful interventions.

Background: Serum thyroid-stimulating hormone (TSH) measurement is the diagnostic cornerstone for primary thyroid dysfunction. There is high inter-individual but limited intra-individual variation in TSH concentrations, largely due to genetic factors. The currently used wide population-based reference intervals may lead to inappropriate management decisions. Methods: A polygenic score (PGS) including 59 genetic variants was used to calculate genetically determined TSH reference ranges in a thyroid disease-free cohort (n = 6,834). Its effect on reclassification of diagnoses was investigated when compared to using population-based reference ranges. Next, results were validated in a second independent population-based thyroid disease-free cohort (n = 3,800). Potential clinical implications were assessed in a third independent population-based cohort including individuals without thyroid disease (n = 26,321) as well as individuals on levothyroxine (LT4) treatment (n = 1,132). Results: PGS was a much stronger predictor of individual TSH concentrations than FT4 (total variance in TSH concentrations explained 9.2-11.1% vs. 2.4-2.7%, respectively) or any other nongenetic factor (total variance in TSH concentrations explained 0.2-1.8%). Genetically determined TSH reference ranges differed significantly between PGS quartiles in all cohorts, while the differences in FT4 concentrations were absent or only minor. Up to 24.7-30.1% of individuals, previously classified as having subclinical hypo- and hyperthyroidism when using population-based TSH reference ranges, were reclassified as euthyroid when genetically determined TSH reference ranges were applied. Individuals in the higher PGS quartiles had a higher probability of being prescribed LT4 treatment compared to individuals from the lower PGS quartiles (3.3% in Q1 vs. 5.2% in Q4, Pfor trend =1.7 × 10-8). Conclusions: Individual genetic profiles have the potential to personalize TSH reference ranges, with large effects on reclassification of diagnosis and LT4 prescriptions. As the currently used PGS can only predict approximately 10% of inter-individual variation in TSH concentrations, it should be further improved when more genetic variants determining TSH concentrations are identified in future studies.

Subclinical hypothyroidism (SCH) is a heterogeneous clinical condition ranging from asymptomatic to wide variety of clinical manifestations, which are often nonspecific. Being a common laboratory finding, clinicians often face the dilemma of whether to treat or not. Threshold of 10 mIU/L of thyroid-stimulating hormone (TSH) is often used as a cutoff limit to offer treatment. However, still, debate remains on whether to treat less than 10 mIU/L considering special clinical conditions like pregnancy. Whether SCH exists, is screening needed in asymptomatic individuals, is treating asymptomatic cases beneficial or harmful and what threshold level of TSH to be considered for treatment are all potential questions that need to be answered.

Primary hypothyroidism affects about 3% of the general population in Europe. In most cases people with hypothyroidism are treated with levothyroxine. In the context of the 2023 British Thyroid Association guidance and the 2020 Competitions and Marketing Authority (CMA) ruling, we examined prescribing data for levothyroxine, Natural desiccated thyroid (NDT) and liothyronine by dose, regarding changes over the years 2016-2022.

Monthly primary care prescribing data for each British National Formulary code were analysed for levothyroxine, liothyronine and NDT.

The rolling 12-month total/average of cost or prescribing volume was used to identify the moment of change. Results included number of prescriptions, the actual costs, and the cost/prescription/mcg of drug.

Liothyronine: In 2016 94% of the total 74,500 prescriptions were of the 20 mcg dose. In 2020 the percentage prescribed in the 5 mcg and 10 mcg doses started to increase so that by 2022 each reached nearly 27% of total liothyronine prescribing. The average cost/prescription in 2016 of 20 mcg was £404/prescription and this fell by 80% to £101 in 2022; while the 10 mcg cost of £348/prescription fell by only 35% to £255 and the 5 mcg cost of £355/prescription fell by 38% to £242/prescription. The total prescriptions of liothyronine in 2016 were 74,605, falling by 30% up to 2019 when they started to grow again - most recently at 60,990-15% lower than the 2016 figure, with the result that total costs fell by 70% to £9 m/year.

Liothyronine costs fell after the CMA ruling but remain orders of magnitude higher than for levothyroxine. The remaining 0.2% of patients with liothyronine treated hypothyroidism are still absorbing 16% of medication costs. The lower liothyronine 5cmg and 10 mcg doses as recommended by BTA are 240% the costs of the 20 mcg dose. Thus, following latest BTA guidance which recommends the lower liothyronine doses still incurs substantial additional costs vs the prescribing liothyronine in the no longer recommended treatment regime. High drug price continues to impact clinical decisions, potentially limiting liothyronine therapy availability to a considerable number of patients who could benefit from this treatment.

Background: The benefit of levothyroxine treatment of subclinical hypothyroidism (SCH) is subject to debate. This study compared treatment satisfaction between older adults with SCH using levothyroxine or placebo. Methods: We analyzed pooled individual participant data from two randomized, double-blind, placebo-controlled trials investigating the effects of levothyroxine treatment in older adults with SCH. Community-dwelling participants aged ≥65 years, with SCH (persistent thyrotropin levels 4.60-19.99 mIU/L for >3 months and normal free T4 level), were included. Intervention dose titration until thyrotropin levels normalized, with a mock dose adjustment of placebo. Treatment satisfaction was determined during the final study visit using the Treatment Satisfaction Questionnaire for Medication (TSQM), encompassing perceived effectiveness, side effects, convenience, and global satisfaction, along with the participants' desire to continue study medication after the trial. Results: We included 536 participants. At baseline, the median (interquartile range [IQR]) age was 74.9 (69.7-81.4) years, and 292 (55%) were women. The median (IQR) thyrotropin levels were 5.80 (5.10-7.00) mIU/L at baseline in both groups; at final visit, 4.97 (3.90-6.35) mIU/L in the placebo and 3.24 (2.49-4.41) mIU/L in the levothyroxine group. After treatment, the groups did not differ significantly in global satisfaction (mean difference [CI] -1.1 [-4.5 to 2.1], p = 0.48), nor in any other domain of treatment satisfaction. These results held true regardless of baseline thyrotropin levels or symptom burden. No major differences were found in the numbers of participants who wished to continue medication after the trial (levothyroxine 35% vs. placebo 27%), did not wish to continue (levothyroxine 27% vs. placebo 30%), or did not know (levothyroxine 37% vs. placebo 42%) (p = 0.14). In a subpopulation with high symptom burden from hypothyroid symptoms at baseline, those using levothyroxine more often desired to continue the medication after the trial than those using placebo (mean difference [CI]: -21.1% [-35.6% to -6.5%]). Conclusion: These pooled data from two RCTs showed no major differences in treatment satisfaction between older adults receiving levothyroxine or placebo. This finding has important implications for decision-making regarding initiating levothyroxine treatment for SCH. Our findings generally support refraining from routinely prescribing levothyroxine in older adults with SCH.

Background: Hypothyroidism is common, however, aspects of its treatment remain controversial. Our survey aimed at documenting treatment choices of European thyroid specialists and exploring how patients' persistent symptoms, clinician demographics, and geo-economic factors relate to treatment choices. Methods: Seventeen thousand two hundred forty-seven thyroid specialists from 28 countries were invited to participate in an online questionnaire survey. The survey included respondent demographic data and treatment choices for hypothyroid patients with persistent symptoms. Geo-economic data for each country were included in the analyses. Results: The response rate was 32.9% (6058 respondents out of 17,247 invitees). Levothyroxine (LT4) was the initial treatment preferred by the majority (98.3%). Persistent symptoms despite normal serum thyrotropin (TSH) while receiving LT4 treatment were reported to affect up to 10.0% of patients by 75.4% of respondents, while 28.4% reported an increasing such trend in the past 5 years. The principal explanations offered for patients' persistent symptoms were psychosocial factors (77.1%), comorbidities (69.2%), and unrealistic patient expectations (61.0%). Combination treatment with LT4+liothyronine (LT3) was chosen by 40.0% of respondents for patients who complained of persistent symptoms despite a normal TSH. This option was selected more frequently by female thyroid specialists, with high-volume practice, working in countries with high gross national income per capita. Conclusions: The perception of patients' dissatisfaction reported by physicians seems lower than that described by hypothyroid patients in previous surveys. LT4+LT3 treatment is used frequently by thyroid specialists in Europe for persistent hypothyroid-like symptoms even if they generally attribute such symptoms to nonendocrine causes and despite the evidence of nonsuperiority of the combined over the LT4 therapy. Pressure by dissatisfied patients on their physicians for LT3-containing treatments is a likely explanation. The association of the therapeutic choices with the clinician demographic characteristics and geo-economic factors in Europe is a novel information and requires further investigation.

To investigate general practitioners' course of action after detection of elevated thyroid stimulating hormone (TSH) levels regarding repeat testing, direct levothyroxine replacement, or neither.

We conducted a retrospective study of adults without prior evidence of thyroid disease and with a first detection of elevated TSH levels from January 1, 2015, to December 31, 2020, using data from electronic medical records of a Swiss primary care database. We determined the occurrence of either repeat TSH testing or direct levothyroxine initiation in primary care during 12-month follow-up and determined associations with demographic and clinical factors.

Of the 1 591 patients included (median age 65 years, 64.4% female, median TSH 5.7 mIU/L), 34.3% received repeat TSH testing and 12.4% received direct levothyroxine replacement in primary care during follow-up. Repeat TSH testing showed the strongest association with overt hypothyroidism and was more common among patients with high primary care utilization and among patients aged 40-64 years compared to patients aged <40 years. Direct levothyroxine initiation was more likely for TSH levels >7 mIU/L, overt hypothyroidism, female patients, and nonurban practices.

While the degree of thyroid dysfunction was the main driver of follow-up, we identified important gaps in the primary care-based monitoring of elevated TSH levels in young patients and in patients with infrequent consultations. We also observed potential overtreatment of women and patients in nonurban areas. Our findings highlight the need for standardization and dissemination of guidelines for the management of elevated TSH levels among general practitioners.

With age, the prevalence of subclinical hypothyroidism rises. However, incidence and determinants of spontaneous normalization remain largely unknown.

To investigate incidence and determinants of spontaneous normalization of TSH levels in older adults with subclinical hypothyroidism.

Pooled data were used from the (1) pretrial population and (2) in-trial placebo group from 2 randomized, double-blind, placebo-controlled trials (Thyroid Hormone Replacement for Untreated Older Adults With Subclinical Hypothyroidism Trial and Institute for Evidence-Based Medicine in Old Age thyroid 80-plus thyroid trial).

Community-dwelling 65+ adults with subclinical hypothyroidism from the Netherlands, Switzerland, Ireland, and the United Kingdom.

The pretrial population (N = 2335) consisted of older adults with biochemical subclinical hypothyroidism, defined as ≥1 elevated TSH measurement (≥4.60 mIU/L) and a free T4 within the laboratory-specific reference range. Individuals with persistent subclinical hypothyroidism, defined as ≥2 elevated TSH measurements ≥3 months apart, were randomized to levothyroxine/placebo, of which the in-trial placebo group (N = 361) was included.

Incidence of spontaneous normalization of TSH levels and associations between participant characteristics and normalization.

In the pretrial phase, TSH levels normalized in 60.8% of participants in a median follow-up of 1 year. In the in-trial phase, levels normalized in 39.9% of participants after 1 year of follow-up. Younger age, female sex, lower initial TSH level, higher initial free T4 level, absence of thyroid peroxidase antibodies, and a follow-up measurement in summer were independent determinants for normalization.

Because TSH levels spontaneously normalized in a large proportion of older adults with subclinical hypothyroidism (also after confirmation by repeat measurement), a third measurement may be recommended before considering treatment.

ClinicalTrials.gov, NCT01660126 and Netherlands Trial Register, NTR3851.

Levothyroxine is one of the most prescribed medications in the United States.

This study explores the appropriateness of levothyroxine prescriptions.

A retrospective multicenter study was conducted on adult patients who were prescribed levothyroxine for the first time between 2017 and 2020 at three academic centers in the United States. We classified each case of levothyroxine initiation into one of three mutually exclusive categories: appropriate (clinically supported), indeterminate (clinically unclear), or nonevidence based (NEB, not clinically supported).

A total of 977 participants were included. The mean age was 55 years (SD 19), there was female (69%) and White race predominance (84%), and 44% had possible hypothyroid symptoms. Nearly half of the levothyroxine prescriptions were considered NEB (528, 54%), followed by appropriate (307, 31%) and indeterminate (118, 12%). The most common reason for NEB prescription was an index thyrotropin (TSH) value of less than 10 mIU/L without previous TSH or thyroxine values (131/528, 25%), for appropriate prescription, was overt hypothyroidism (163/307, 53%), and for an indeterminate prescription was a nonconfirmed subclinical hypothyroidism with TSH greater than or equal to 10 mIU/L (no confirmatory testing) (51/118, 43%). In multivariable analysis, being female (odds ratio [OR]: 1.3; 95% CI, 1.0-1.7) and prescription by a primary care provider (OR: 1.5; 95% CI, 1.2-2.0) were associated with NEB prescriptions.

There is a considerable proportion of NEB levothyroxine prescriptions. These results call for additional research to replicate these findings and to explore the perspective of those prescribing and receiving levothyroxine.

Thyroid hormones have vital roles in development, growth and energy metabolism. Within the past two decades, disturbances in thyroid hormone action have been implicated in ageing and the development of age-related diseases. This Review will consider results from biomedical studies that have identified the importance of precise temporospatial regulation of thyroid hormone action for local tissue maintenance and repair. Age-related disturbances in the maintenance of tissue homeostasis are thought to be important drivers of age-related disease. In most iodine-proficient human populations without thyroid disease, the mean, median and 97.5 centile for circulating concentrations of thyroid-stimulating hormone are progressively higher in adults over 80 years of age compared with middle-aged (50-59 years) and younger (20-29 years) adults. This trend has been shown to extend into advanced ages (over 100 years). Here, potential causes and consequences of the altered thyroid status observed in old age and its association with longevity will be discussed. In about 5-20% of adults at least 65 years of age, thyroid-stimulating hormone concentrations are elevated but circulating concentrations of thyroid hormone are within the population reference range, a condition referred to as subclinical hypothyroidism. Results from randomized clinical trials that have tested the clinical benefit of thyroid hormone replacement therapy in older adults with mild subclinical hypothyroidism will be discussed, as well as the implications of these findings for screening and treatment of subclinical hypothyroidism in older adults.

Thyroid hormone is among the most common prescriptions in the US and up to 20% may be overtreated. Endogenous hyperthyroidism may be a risk factor for dementia, but data are limited for iatrogenic thyrotoxicosis.

To determine whether thyrotoxicosis, both endogenous and exogenous, is associated with increased risk of cognitive disorders.

This cohort study performed a longitudinal time-varying analysis of electronic health records for patients receiving primary care in the Johns Hopkins Community Physicians Network between January 1, 2014, and May 6, 2023. Patients 65 years and older with at least 2 visits 30 days apart to their primary care physicians were eligible. None of the 65 931 included patients had a history of low thyrotropin (TSH) level or cognitive disorder diagnoses within 6 months of their first visit. Data analysis was performed from January 1 through August 5, 2023.

The exposure variable was a low TSH level, characterized based on the clinical context as due to endogenous thyrotoxicosis, exogenous thyrotoxicosis, or unknown cause, excluding those attributable to acute illness or other medical factors such as medications.

The outcome measure was cognitive disorders, including mild cognitive impairment and all-cause dementia, to improve sensitivity and account for the underdiagnosis of dementia in primary care.

A total of 65 931 patients were included in the analysis (median [IQR] age at first visit, 68.0 [65.0-74.0] years; 37 208 [56%] were female; 46 106 [69.9%] were White). Patients exposed to thyrotoxicosis had cognitive disorder incidence of 11.0% (95% CI, 8.4%-14.2%) by age 75 years vs 6.4% (95% CI, 6.0%-6.8%) for those not exposed. After adjustment, all-cause thyrotoxicosis was significantly associated with risk of cognitive disorder diagnosis (adjusted hazard ratio, 1.39; 95% CI, 1.18-1.64; P < .001) across age groups. When stratified by cause and severity, exogenous thyrotoxicosis remained a significant risk factor (adjusted hazard ratio, 1.34; 95% CI, 1.10-1.63; P = .003) with point estimates suggestive of a dose response.

In this cohort study among patients 65 years and older, a low TSH level from either endogenous or exogenous thyrotoxicosis was associated with higher risk of incident cognitive disorder. Iatrogenic thyrotoxicosis is a common result of thyroid hormone therapy. With thyroid hormone among the most common prescriptions in the US, understanding the negative effects of overtreatment is critical to help guide prescribing practice.

Thyroid hormone replacement is paramount in overt hypothyroidism; recently, however, thyroid hormone substitution is increasingly prescribed to patients with normal thyroid hormone levels. This forum article discusses the complex causes and the possible negative effects of overusing thyroid hormone replacement drugs.

Approximately 10%-15% of subjects with hypothyroidism on L-thyroxine (LT4) alone have persistent symptoms affecting their quality of life (QoL). Although the cause is unclear, there is evidence that "tissue T3 lack" may be responsible. If so, combining liothyronine (LT3) with LT4 would be helpful. However, randomized controlled trials (RCT), have not established greater efficacy for the LT3 + LT4 combination in these subjects than for LT4 alone. While the trial design may have been responsible, the use of unphysiological, short-acting LT3 preparations and non-thyroid-specific patient-reported outcome measures (PROMs) may have contributed. We recommend attention to the following aspects of trial design for future RCTs of LT3 + LT4 compared to LT4 alone: (a) Subject selection-(i) measurable symptoms (disadvantages should be recognized); (ii) using a validated thyroid specific PROM such as ThyPRO39 or the Composite scale derived from it; (iii) those taking over 1.2 μg/day or 100 μg/day (for pragmatic reasons) of LT4 defining a population likely without intrinsic thyroid activity who depend on exogenous LT4; (iv) recruiting a preponderance of subjects with autoimmune thyroiditis increasing generalisability; and (v) those with a high symptom load with a greater response to combination therapy e.g. those with the deiodinase 2 polymorphism. (b) The use of physiological LT3 preparations producing pharmacokinetic similarities to T3 profiles in unaffected subjects: two long-acting LT3 preparations are currently available and must be tested in phase 2b/3 RCTs. (c) The superiority of a crossover design in limiting numbers and costs while maintaining statistical power and ensuring that all subjects experienced the investigative medication.

Subclinical hypothyroidism is diagnosed when serum thyroid stimulating hormone levels are higher whilst free thyroxine levels remain within their respective reference ranges. These reference ranges are uniformly applied in all adults, despite serum thyroid stimulating hormone levels naturally increasing with age. Research has found that mildly elevated thyroid stimulating hormone levels may be associated with some benefits in ageing patients, including reduced mortality and better cardiorespiratory fitness. Levothyroxine is typically prescribed to patients with hypothyroidism, but no conclusive evidence exists on whether levothyroxine therapy is beneficial or detrimental in older subclinical hypothyroid patients. Despite this, prescriptions for levothyroxine are increasing year-on-year. This study aims to determine if receiving levothyroxine affects the cardiovascular and bone health outcomes of subclinical patients in primary care aged 50 years and over.

This project includes a retrospective cohort analysis and a target trial emulation study using electronic patient records collected between 2006 and 2021 and recorded in The Health Improvement Network database. The primary outcome of this study is to compare the cardiovascular outcomes of subclinical hypothyroid patients aged over 50 years treated with levothyroxine compared to those untreated. Secondary outcomes are bone health and all-cause mortality outcomes. Descriptive and inferential statistics will both be employed to analyse the data. Secondary analysis will explore confounding factors, including age, sex, smoking status, body mass index, co-morbidities, and levothyroxine dosage.

There needs to be a greater understanding of the potential risks of the current treatment for older patients with subclinical hypothyroidism in a primary care setting. We will investigate the clinical importance of this issue and whether older subclinical hypothyroid patients have poorer outcomes when treated. Clarifying this concern may help address the healthcare resource implications of ageing patients being misclassified as having mild hypothyroidism, as these patients are more likely to repeat their blood tests. This could reduce prescription wastage and improve patient outcomes and quality of life in the ageing population.

Not applicable.

Levothyroxine is a very commonly prescribed drug, and treatment with it is often insufficient or excessive. Nonetheless, there have been only a few reports on the determinants of inadequate levothyroxine treatment.

Data from 2938 participants in the population-based Rhineland Study were analyzed. Putative determinants of inadequate levothyroxine treatment (overtreatment, thyrotropin level <0.56 mU/L; undertreatment, thyrotropin level >4.27 mU/L) were studied with logistic regression. The determinants of the levothyroxine dose were assessed with linear regression.

Overall, 23% of the participants (n = 662) stated that they were taking levothyroxine. Among these participants, 18% were overtreated and 4% were undertreated. Individuals over 70 years of age and above were four times as likely to be overtreated (OR = 4.05, 95% CI [1.20; 13.72]). Each rise in the levothyroxine dose by 25 μg was associated with an increased risk of overtreatment (OR = 1.02, 95% CI [1.02; 1.03]) and of undertreatment (OR = 1.02, 95% CI [1.00; 1.03]). Well-controlled participants (normal thyrotropin levels 0.56-4.27 mU/L) received a lower levothyroxine dose (1.04 ± 0.5 μg/kg/d) than overtreated (1.40 ±0.5 μg/kg/d) or undertreated (1.37 ±0.5 μg/kg/d) participants. No association was found between sociodemographic factors or comorbidities and the levothyroxine dose. Iodine supplementation was associated with a lower daily dose (β = -0.19, 95% CI [-0.28; -0.10]), while three years or more of levothyroxine exposure was associated with a higher daily dose (β = 0.24, 95% CI [0.07; 0.41]).

Levothyroxine intake was high in our sample, and suboptimal despite monitoring. Our findings underscore the need for careful dosing and for due consideration of deintensification of treatment where appropriate.

In gender-skewed conditions such as Graves' disease (GD), the outcome naturally becomes dominated by the majority. This may lead to gender-biased misunderstandings regarding treatment outcomes. This especially holds true when complications, such as depression, are unevenly distributed. We have, therefore, studied the long-term outcome of GD from a gender perspective.

A cohort of 1186 patients with GD was included in a follow-up 6-10 years after inclusion. Choice of treatment, the feeling of recovery, long-term treatment, comorbidity, and quality of life were investigated with questionnaires. All results were studied sex-divided.

We included 973 women and 213 men. There was no difference between men and women in the choice of treatment. At follow-up, women scored significantly worse in the general questionnaire 36-item Short-Form Health Status (SF-36) domain bodily pain and in the thyroid-specific Thyroid-Related Patient-Reported Outcome (ThyPRO) domains depression, impaired sex life, and cosmetic complaints, all p < 0.05. Women were twice as likely (29.5%) to be treated with levothyroxine after successful treatment with antithyroid drugs (ATD) compared with men (14.9%, p < 0.05).

After treatment for GD, women were more affected by depression, impaired sex life, cosmetic issues, and bodily pain despite successful cure of hyperthyroidism. The prevalence of hypothyroidism was also doubled in women. Whether these observed gender differences reflect a worse outcome of GD in women or a natural consequence of a higher prevalence of these symptoms and autoimmunity in the female population is difficult to disentangle. Nevertheless, several years after GD, women reveal more persistent symptoms.

Reference intervals of thyroid-stimulating hormone (TSH) and free thyroxine (FT4) are statistically defined by the 2·5-97·5th percentiles, without accounting for potential risk of clinical outcomes. We aimed to define the optimal healthy ranges of TSH and FT4 based on the risk of cardiovascular disease and mortality.

This systematic review and individual participant data (IPD) meta-analysis identified eligible prospective cohorts through the Thyroid Studies Collaboration, supplemented with a systematic search via Embase, MEDLINE (Ovid), Web of science, the Cochrane Central Register of Controlled Trials, and Google Scholar from Jan 1, 2011, to Feb 12, 2017 with an updated search to Oct 13, 2022 (cohorts found in the second search were not included in the IPD). We included cohorts that collected TSH or FT4, and cardiovascular outcomes or mortality for adults (aged ≥18 years). We excluded cohorts that included solely pregnant women, individuals with overt thyroid diseases, and individuals with cardiovascular disease. We contacted the study investigators of eligible cohorts to provide IPD on demographics, TSH, FT4, thyroid peroxidase antibodies, history of cardiovascular disease and risk factors, medication use, cardiovascular disease events, cardiovascular disease mortality, and all-cause mortality. The primary outcome was a composite outcome including cardiovascular disease events (coronary heart disease, stroke, and heart failure) and all-cause mortality. Secondary outcomes were the separate assessment of cardiovascular disease events, all-cause mortality, and cardiovascular disease mortality. We performed one-step (cohort-stratified Cox models) and two-step (random-effects models) meta-analyses adjusting for age, sex, smoking, systolic blood pressure, diabetes, and total cholesterol. The study was registered with PROSPERO, CRD42017057576.

We identified 3935 studies, of which 53 cohorts fulfilled the inclusion criteria and 26 cohorts agreed to participate. We included IPD on 134 346 participants with a median age of 59 years (range 18-106) at baseline. There was a J-shaped association of FT4 with the composite outcome and secondary outcomes, with the 20th (median 13·5 pmol/L [IQR 11·2-13·9]) to 40th percentiles (median 14·8 pmol/L [12·3-15·0]) conveying the lowest risk. Compared with the 20-40th percentiles, the age-adjusted and sex-adjusted hazard ratio (HR) for FT4 in the 80-100th percentiles was 1·20 (95% CI 1·11-1·31) for the composite outcome, 1·34 (1·20-1·49) for all-cause mortality, 1·57 (1·31-1·89) for cardiovascular disease mortality, and 1·22 (1·11-1·33) for cardiovascular disease events. In individuals aged 70 years and older, the 10-year absolute risk of composite outcome increased over 5% for women with FT4 greater than the 85th percentile (median 17·6 pmol/L [IQR 15·0-18·3]), and men with FT4 greater than the 75th percentile (16·7 pmol/L [14·0-17·4]). Non-linear associations were identified for TSH, with the 60th (median 1·90 mIU/L [IQR 1·68-2·25]) to 80th percentiles (2·90 mIU/L [2·41-3·32]) associated with the lowest risk of cardiovascular disease and mortality. Compared with the 60-80th percentiles, the age-adjusted and sex-adjusted HR of TSH in the 0-20th percentiles was 1·07 (95% CI 1·02-1·12) for the composite outcome, 1·09 (1·05-1·14) for all-cause mortality, and 1·07 (0·99-1·16) for cardiovascular disease mortality.

There was a J-shaped association of FT4 with cardiovascular disease and mortality. Low concentrations of TSH were associated with a higher risk of all-cause mortality and cardiovascular disease mortality. The 20-40th percentiles of FT4 and the 60-80th percentiles of TSH could represent the optimal healthy ranges of thyroid function based on the risk of cardiovascular disease and mortality, with more than 5% increase of 10-year composite risk identified for FT4 greater than the 85th percentile in women and men older than 70 years. We propose a feasible approach to establish the optimal healthy ranges of thyroid function, allowing for better identification of individuals with a higher risk of thyroid-related outcomes.

None.

Replacement of thyroid hormones (TH) with Levothyroxine (LT4) is the treatment of choice for hypothyroidism, however, there are aspects of treatment where uncertainties exist and practice varies. Factors influencing initiation and choice of TH replacement may impact patient satisfaction, safety, and health care costs.

The aim of the study was to examine the attitudes of Irish endocrinologists regarding the treatment of hypothyroid and euthyroid patients with TH. Members of the Irish Endocrine Society (IES) were invited to participate in an online survey.

Forty-eight invitations were sent, and 39 (81.3%) participants responded. All respondents favoured LT4 tablet therapy for treatment of hypothyroidism, but 20.5% prescribed combination therapy (LT4 and liothyronine), and 13% regularly used desiccated thyroid extract. A significant proportion (51%) might prescribe TH in euthyroid patients; 41% for thyroid auto-antibody positive women seeking pregnancy, 18% for goitre and 5% for unexplained fatigue. Many (38%) consider combination therapy in patients with persistent symptoms. Respondents reported seeing LT4 treated patients with persistent symptomatology more frequently and perceive psychosocial factors and comorbidities to be the most common reasons for such symptoms.

LT4 tablets are the treatment of choice for hypothyroidism in Ireland. Approximately a third of Irish endocrinologists either regularly use, or would consider, liothyronine for hypothyroid patients. A significant proportion would give TH to euthyroid individuals in specific circumstances. The prescription of TH amongst Irish endocrinologists was generally in keeping with recommended practice, and areas where practice deviated from guidance were typically where evidence was conflicting or insufficient.

Hypothyroidism means an underactive thyroid gland. This leads to a decrease in the functioning of the thyroid gland. It is a very common endocrine disorder that causes under-secretion of thyroid hormones, mainly thyroxine (T4) and triiodothyronine (T3). It affects people of every age group but is more commonly found in women and older people. The symptoms of hypothyroidism can go unnoticed, may not be specific, and may overlap with other conditions, which makes it harder to diagnose it in some cases. Common symptoms include fatigue, weight gain, increased sensitivity to cold (cold intolerance), irregular bowel movements (constipation), and dry skin (xeroderma). These conditions are mostly the result of a low metabolic rate in the body. Weight gain occurs due to a decrease in fat-burning rate and cold intolerance due to a decrease in heat production by the body. This condition can be caused by a variety of factors, including autoimmune diseases, radiation therapy, thyroid gland removal surgeries, and certain medications. The diagnosis of hypothyroidism is based on laboratory tests that measure the levels of thyroid hormones (T3 and T4) in the blood. Treatment typically involves lifelong hormone replacement therapy with synthetic thyroid hormone replacement medication, such as levothyroxine, to help regulate hormone levels in the body. People with hypothyroidism may need to have their medication dosage adjusted over time. If hypothyroidism is left untreated, it can lead to severe complications like mental retardation, delayed milestones, etc., in infants and heart failure, infertility, myxedema coma, etc., in adults. With appropriate treatment, the symptoms of hypothyroidism can be effectively managed, and most people with the condition can lead normal, healthy lives. Lifestyle modifications like eating healthy food and exercising regularly can help manage the symptoms and improve the quality of life.

The objective was to explore the management of newly diagnosed hypothyroidism in adults regarding laboratory diagnostics and treatment in Region Halland (RH). In addition, to investigate whether current recommendations were followed regarding diagnostics.

Retrospective observational study.

A population-based study utilizing healthcare registry data from all public primary health care (PHC) clinics in RH during 2014-2019.

Newly diagnosed patients with hypothyroidism according to ICD-10, aged ≥18 years when diagnosed and living and receiving health care in RH. There were 2494 patients included in the study.

Registrations of thyroid laboratory values, diagnostic codes, and drug treatment was collected. Demographic data were also recorded. Laboratory values were checked also after 12-24 months after initial diagnosis. The main outcome was the proportion with elevated TSH and TPO and how the TSH value had changed at the follow-up.

There were 1431 (61%) patients who had elevated TSH at the onset of the disease and TPO was tested in 1133 (46%) of the patients. Elevated TPO was found in 566 (23%) of the patients. After one year, there were 1908 (76%) patients who obtained a prescription for levothyroxine. In 1127 (45%) patients, TSH had normalized within one year.

There were 39% of the patients diagnosed with hypothyroidism despite normal or subclinical TSH. There was an underuse of TPO in diagnosis and this advocated that the criteria for diagnostics according to current guidelines be followed to avoid unnecessary treatment.