Association of insulin resistance with serum ferritin and aminotransferases-iron hypothesis

Table 4 Serum ferritin concentration and estimated insulin sensitivity indices by quintile of inflammatory marker - C-reactive protein

	Quintile 1	Quintile 2	Quintile 3	Quintile 4	Quintile 5	P1	P2	P3
Serum ferritin concentration (mcg/L)
Non-Hispanic white males	142 (130, 155)	157 (144, 170)	179 (164, 195)	201 (180, 222)	201 (181, 221)	< 0.000001	0.000002	0.000005
Non-Hispanic white females	19 (18, 20)	49 (48, 50)	120 (116, 125)	152 (134, 171)	108 (95, 120)	0.000003	0.00003	0.00003
Non-Hispanic black males	186 (163, 209)	187 (167, 207)	267 (236, 298)	227 (202, 253)	254 (281, 228)	NS	NS	NS
Non-Hispanic black females	90 (74, 106)	79 (66, 91)	77 (65, 89)	102 (87, 118)	115 (98, 132)	0.002	0.0009	0.001
Hispanic males	150 (134, 166)	157 (135, 179)	161 (137, 185)	157 (136, 178)	172 (154, 191)	NS	NS	NS
Hispanic females	52 (44, 60)	56 (48, 64)	63 (53, 72)	72 (60, 84)	92 (68, 115)	0.00001	0.007	0.006
Insulin sensitivity by the homeostasis model assessment (%S)4
Non-Hispanic white males	0.541 (0.505, 0.578)	0.531 (0.500, 0.562)	0.546 (0.509, 0.582)	0.459 (0.425, 0.494)	0.412 (0.383, 0.440)	< 0.000001	0.05	0.03
Non-Hispanic white females	0.684 (0.651, 0.718)	0.627 (0.592, 0.661)	0.596 (0.558, 0.634)	0.494 (0.461, 0.526)	0.422 (0.392, 0.452)	< 0.000001	0.004	0.004
Non-Hispanic black males	0.562 (0.517, 0.607)	0.572 (0.526, 0.618)	0.561 (0.499, 0.623)	0.549 (0.488, 0.611)	0.478 (0.426, 0.530)	0.05	NS	NS
Non-Hispanic black females	0.524 (0.489, 0.558)	0.524 (0.487, 0.560)	0.497 (0.464, 0.530)	0.404 (0.369, 0.438)	0.327 (0.288, 0.365)	< 0.000001	0.004	0.002
Hispanic males	0.558 (0.507, 0.608)	0.484 (0.438, 0.530)	0.525 (0.472, 0.578)	0.513 (0.460, 0.566)	0.372 (0.334, 0.411)	0.00001	NS	NS
Hispanic females	0.538 (0.495, 0.582)	0.53 (0.481, 0.579)	0.471 (0.430, 0.513)	0.392 (0.355, 0.429)	0.353 (0.319, 0.387)	< 0.000001	NS	NS
Insulin sensitivity by the simple QUICKI5
Non-Hispanic white males	0.342 (0.339, 0.346)	0.342 (0.339, 0.345)	0.342 (0.339, 0.346)	0.332 (0.328, 0.336)	0.328 (0.325, 0.331)	< 0.000001	0.01	0.008
Non-Hispanic white females	0.356 (0.354, 0.359)	0.351 (0.348, 0.354)	0.347 (0.343, 0.350)	0.336 (0.333, 0.340)	0.328 (0.324, 0.331)	< 0.000001	0.004	0.005
Non-Hispanic black males	0.345 (0.341, 0.349)	0.345 (0.340, 0.349)	0.341 (0.336, 0.346)	0.34 (0.334, 0.345)	0.332 (0.327, 0.338)	0.01	NS	NS
Non-Hispanic black females	0.341 (0.337, 0.345)	0.341 (0.337, 0.345)	0.339 (0.335, 0.342)	0.327 (0.323, 0.331)	0.314 (0.310, 0.319)	< 0.000001	0.000002	0.000001
Hispanic males	0.342 (0.338, 0.347)	0.335 (0.331, 0.340)	0.338 (0.333, 0.343)	0.338 (0.333, 0.342)	0.321 (0.317, 0.326)	< 0.000001	NS	NS
Hispanic females	0.342 (0.338, 0.346)	0.34 (0.336, 0.344)	0.334 (0.329, 0.338)	0.325 (0.321, 0.329)	0.319 (0.314, 0.323)	< 0.000001	0.02	0.03

Data presented mean with 95%CI. ¹P values for trend, unadjusted; ²P values for trend, after adjustment for age and body mass index; ³P values for trend, after adjustment for age, body mass index, alcohol consumption, and mineral/iron supplement;

⁴%S = 22.5/(fasting insulin concentration in mU/L × fasting glucose concentration in mmol/L);

⁵Quicki = 1/[log(fasting glucose concentration in mg/dL) + log(fasting insulin concentration in mU/L)]. NS: Not significant; QUICKI: Quantitative insulin sensitivity check index.