Table 1.
Characteristics of 488 White HEIRS Study Participants
| Characteristica |
HFE C282Y homozygotes (n = 176; 64.2% F) |
HFE wt/wt controls (n = 312; 60.6% F) |
p-valueb |
|---|---|---|---|
| Mean age ± 1 SD (range), years | 50 ± 13 | 55 ± 14 | <0.0001 |
| Mean TSH, mIU/L (95% CI) | 1.67 (1.42, 1.96) | 2.00 (1.80, 2.22) | 0.0652 |
| TSH <0.400 mIU/L, % (n) | 5.1 (9) | 2.9 (9) | 0.2097 |
| TSH >5.00 mIU/L, % (n) | 8.0 (14) | 8.3 (26) | 0.8835 |
| Mean free T4, ng/dLc (95% CI) | 1.12 (1.09, 1.15) | 1.01 (1.05, 1.10) | 0.0492 |
| Free T4 <0.70 ng/dL, % (n) | 1.7 (3) | 1.0 (3) | 0.3741 |
| Free T4 >1.85 ng/dL, % (n) | 1.7 (3) | 1.3 (4) | 0.4925 |
| TSH <0.400 mIU/L and free T4 >1.85 ng/dL, % (n) | 0 | 1.0 (3) | 0.2604 |
| TSH >5.00 mIU/L and free T4 <0.70 ng/dL, % (n) | 1.7 (3) | 1.3 (4) | 0.4925 |
| Mean SF, ng/mL (95% CI) | 308 (252, 376) | 77 (71, 84) | <0.0001 |
a
TSH, thyroid-stimulating hormone; T4, thyroxine; SF, serum ferritin. For display of TSH values, we used three significant figures.
b
Comparisons were made between HFE C282Y homozygotes and HFE wt/wt controls using Student's t-tests, Fisher exact tests, or chi-square tests, as appropriate.
c
When mean log10 free T4 was computed in C282Y homozygotes and in controls after all participants with free T4 values outside the reference range of 0.70–1.85 ng/dL were removed, a slightly higher mean was still observed in C282Y homozygotes (p = 0.0423).