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

Table 6 Serum ferritin concentration and estimated insulin sensitivity indices by quintile of gamma glutamyl transferase

	Quintile 1	Quintile 2	Quintile 3	Quintile 4	Quintile 5	P1	P2	P3
Serum ferritin concentration (mcg/L)
Non-Hispanic white males	141 (125, 157)	146 (131,161)	174 (156, 191)	179 (162, 196)	227 (204, 250)	< 0.000001	< 0.000001	< 0.000001
Non-Hispanic white females	55 (48, 62)	70 (61, 78)	95 (81, 110)	92 (77, 107)	137 (121, 154)	< 0.000001	< 0.000001	< 0.000001
Non-Hispanic black males	165 (144, 187)	191 (163, 219)	221 (195, 247)	220 (194, 246)	298 (263, 333)	< 0.000001	< 0.000001	< 0.000001
Non-Hispanic black females	60 (45, 74)	79 (68, 91)	84 (67, 100)	97 (83, 112)	141 (119, 163)	< 0.000001	< 0.000001	< 0.000001
Hispanic males	105 (93, 117)	137 (121, 153)	152 (132, 172)	173 (144, 202)	240 (208, 272)	< 0.000001	< 0.000001	< 0.000001
Hispanic females	38 (30, 47)	38 (32, 44)	59 (47, 70)	82 (70, 93)	109 (90, 129)	< 0.000001	< 0.000001	< 0.000001
Insulin sensitivity by the homeostasis model assessment (%S)4
Non-Hispanic white males	0.622 (0.584, 0.659)	0.521 (0.486, 0.556)	0.5061 (0.465, 0.546)	0.422 (0.387, 0.458)	0.402 (0.367, 0.436)	< 0.000001	< 0.000001	< 0.000001
Non-Hispanic white females	0.732 (0.695, 0.769)	0.648 (0.609, 0.686)	0.587 (0.547, 0.626)	0.48 (0.444, 0.516)	0.397 (0.361, 0.433)	< 0.000001	< 0.000001	< 0.000001
Non-Hispanic black males	0.607 (0.560, 0.654)	0.588 (0.522, 0.653)	0.537 (0.491, 0.583)	0.489 (0.429, 0.548)	0.462 (0.404, 0.520)	0.0001	NS	0.05
Non-Hispanic black females	0.554 (0.515, 0.594)	0.454 (0.419, 0.489)	0.45 (0.409, 0.491)	0.407 (0.372, 0.442)	0.383 (0.332, 0.434)	< 0.000001	0.0002	0.00002
Hispanic males	0.67 (0.625, 0.715)	0.562 (0.486, 0.638)	0.423 (0.383, 0.463)	0.439 (0.376, 0.501)	0.359 (0.299, 0.419)	< 0.000001	0.00005	0.000005
Hispanic females	0.623 (0.569, 0.677)	0.494 (0.448, 0.539)	0.424 (0.381, 0.466)	0.338 (0.301, 0.375)	0.343 (0.298, 0.389)	< 0.000001	0.000002	0.000003
Insulin sensitivity by the simple QUICKI5
Non-Hispanic white males	0.351 (0.348, 0.354)	0.341 (0.338, 0.344)	0.339 (0.335, 0.342)	0.328 (0.324, 0.332)	0.325 (0.321, 0.330)	< 0.000001	< 0.000001	< 0.000001
Non-Hispanic white females	0.361 (0.358, 0.364)	0.353 (0.350, 0.356)	0.347 (0.344, 0.350)	0.335 (0.332, 0.339)	0.323 (0.319, 0.327)	< 0.000001	< 0.000001	< 0.000001
Non-Hispanic black males	0.349 (0.345, 0.353)	0.344 (0.338, 0.350)	0.342 (0.337, 0.346)	0.334 (0.328, 0.339)	0.331 (0.325, 0.337)	< 0.000001	0.01	0.004
Non-Hispanic black females	0.345 (0.341, 0.348)	0.334 (0.330, 0.338)	0.332 (0.328, 0.337)	0.327 (0.323, 0.332)	0.321 (0.315, 0.326)	< 0.000001	< 0.000001	< 0.000001
Hispanic males	0.356 (0.352, 0.360)	0.341 (0.335, 0.347)	0.330 (0.325, 0.334)	0.329 (0.323, 0.334)	0.318 (0.312, 0.324)	< 0.000001	< 0.000001	< 0.000001
Hispanic females	0.351 (0.346, 0.355)	0.338 (0.334, 0.342)	0.329 (0.325, 0.334)	0.318 (0.313, 0.323)	0.316 (0.311, 0.322)	< 0.000001	< 0.000001	< 0.000001

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.