Table 4—

Adjusted* ratio (95% CI) of mean insulin resistance parameters for increasing quartiles of serum ferritin in nondiabetic U.S. adults

Premenopausal women (n = 1,612)Quartile of serum ferritin
≤20 μg/l21–36 μg/l37–60 μg/l>60 μg/lP (trend)
Median ferritin in quartile11264789
HOMA-IR1 (reference)0.91 (0.83–0.99)1.03 (0.89–1.06)0.97 (0.87–1.03)0.98
Fasting insulin (pmol/l)1 (reference)0.92 (0.86–1.03)1.02 (0.90–1.06)0.96 (0.88–1.03)0.99
Triglyceride-to-HDL ratio1 (reference)1.03 (0.90–1.19)1.05 (0.89–1.23)1.09 (0.96–1.23)0.12
Postmenopausal women (n = 1,234)Quartile of serum ferritin
≤54 μg/l55–95 μg/l96–168 μg/l>168 μg/lP (trend)
Median ferritin in quartile3573125212
HOMA-IR1 (reference)0.95 (0.88–1.02)1.13 (1.04–1.23)1.21 (1.12–1.30)<0.001
Fasting insulin (pmol/l)1 (reference)0.96 (0.89–1.02)1.10 (1.03–1.19)1.19 (1.09–1.26)<0.001
Triglyceride-to-HDL ratio1 (reference)0.89 (0.79–0.99)1.03 (0.89–1.19)1.27 (1.10–1.48)<0.001
Men (n = 2,618)Quartile of serum ferritin
≤86 μg/l87–145 μg/l146–231 μg/l>231 μg/lP (trend)
Median ferritin in quartile62113182318
HOMA-IR1 (reference)1.01 (0.93–1.09)1.04 (0.97–1.13)1.09 (1.00–1.18)0.04
Fasting insulin (pmol/l)1 (reference)1.01 (0.94–1.08)1.02 (0.95–1.09)1.05 (0.99–1.13)0.08
Triglyceride-to-HDL ratio1 (reference)1.01 (0.88–1.16)1.08 (0.97–1.21)1.21 (1.05–1.40)<0.001
  • *

    * Adjusted for age, race/ethnicity, CRP, smoking, alcohol intake, and BMI. The table represents the ratio of the geometric mean of IR parameters in a given quartile of serum ferritin with respect to the first quartile. For instance, premenopausal women in the second quartile of serum ferritin had HOMA-IR 9% lower than premenopausal women in the first quartile (ratio of means 0.91).