Table 3.
The 2.5th and 97.5th Percentiles of TSH, FT4, and FT3 by Measures of Iodine Status (Adjusted Models)
| UIC, μg/L | ||||||
|---|---|---|---|---|---|---|
| <30 | 30–59.9 | 60–99.9 | 100–150 | >150 | p-Valuea | |
| n | 507 | 625 | 629 | 444 | 372 | |
| UIC, median (IQR), μg/L | 20 (14, 25) | 44 (37, 51) | 78 (69, 88) | 121 (110, 135) | 195 (167, 260) | |
| Plasma TSH, mU/L | ||||||
| 2.5th percentile [95% CI] | 0.48 [0.39, 0.58] | 0.40 [0.32, 0.49] | 0.37 [0.29, 0.45] | 0.39 [0.29, 0.49] | 0.36 [0.25, 0.46] | 0.36 |
| 97.5th percentile [95% CI] | 2.54 [2.32, 2.76] | 2.57 [2.36, 2.77] | 2.82 [2.61, 3.02] | 2.76 [2.52, 3.00] | 2.87 [2.60, 3.13] | 0.16 |
| Plasma FT4, pmol/L | ||||||
| 2.5th percentile [95% CI] | 10.4 [10.2, 10.6] | 10.6 [10.4, 10.7] | 10.4 [10.2, 10.6] | 10.4 [10.2, 10.7] | 10.2 [10.0, 10.5] | 0.29 |
| 97.5th percentile [95% CI] | 15.9 [14.9, 16.9] | 15.6 [14.7, 16.5] | 16.2 [15.3, 17.1] | 15.2 [14.2, 16.3] | 15.2 [14.0, 16.4] | 0.58 |
| Plasma FT3, pmol/L | ||||||
| 2.5th percentile [95% CI] | 4.14 [4.04, 4.24] | 4.08 [3.98, 4.17] | 4.07 [3.98, 4.16] | 4.05 [3.94, 4.15] | 4.02 [3.90, 4.15] | 0.62 |
| 97.5th percentile [95% CI] | 6.08 [5.89, 6.26] | 5.90 [5.73, 6.06] | 5.92 [5.75, 6.10] | 5.97 [5.77, 6.17] | 5.77 [5.55, 5.98] | 0.30 |
| Creatinine-adjusted UIC (UIC∼Cr), μg/L | ||||||
|---|---|---|---|---|---|---|
| <45 | 45–69.9 | 70–89.9 | 90–130 | >130 | p-Valuea | |
| n | 428 | 700 | 580 | 459 | 410 | |
| UIC∼Cr, median (IQR), μg/L | 30 (20, 38) | 60 (53, 65) | 78 (73, 83) | 105 (97, 116) | 172 (143, 227) | |
| Plasma TSH, mU/L | ||||||
| 2.5th percentile [95% CI] | 0.47 [0.36, 0.58] | 0.40 [0.32, 0.48] | 0.38 [0.29, 0.47] | 0.39 [0.29, 0.49] | 0.41 [0.30, 0.51] | 0.80 |
| 97.5th percentile [95% CI] | 2.56 [2.31, 2.82] | 2.62 [2.42, 2.81] | 2.77 [2.56, 2.99] | 2.78 [2.54, 3.02] | 2.78 [2.53, 3.04] | 0.56 |
| Plasma FT4, pmol/L | ||||||
| 2.5th percentile [95% CI] | 10.6 [10.4, 10.8] | 10.3 [10.2, 10.5] | 10.5 [10.3, 10.6] | 10.4 [10.2, 10.6] | 10.3 [10.1, 10.5] | 0.36 |
| 97.5th percentile [95% CI] | 16.0 [14.8, 17.2] | 15.5 [14.6, 16.4] | 16.2 [15.3, 17.2] | 15.6 [14.6, 16.7] | 15.3 [14.2, 16.5] | 0.72 |
| Plasma FT3, pmol/L | ||||||
| 2.5th percentile [95% CI] | 4.14 [4.01, 4.28] | 4.09 [3.99, 4.20] | 4.06 [3.94, 4.17] | 4.08 [3.95, 4.21] | 4.02 [3.89, 4.16] | 0.77 |
| 97.5th percentile [95% CI] | 6.05 [5.80, 6.29] | 5.95 [5.77, 6.13] | 5.97 [5.77, 6.17] | 5.84 [5.62, 6.06] | 5.82 [5.58, 6.05] | 0.61 |
| Iodine from food, μg/day (restricted to supplement nonusers) | ||||||
|---|---|---|---|---|---|---|
| <100 | 100–150 | >150 | p-Valuea | |||
| n | 523 | 562 | 457 | |||
| Iodine intake, median (IQR), μg/day | 77 (62, 89) | 123 (111, 135) | 183 (163, 217) | |||
| Plasma TSH, mU/L | ||||||
| 2.5th percentile [95% CI] | 0.49 [0.40, 0.59] | 0.41 [0.32, 0.49] | 0.43 [0.33, 0.53] | 0.20 | ||
| 97.5th percentile [95% CI] | 2.70 [2.35, 3.05] | 2.78 [2.46, 3.09] | 2.61 [2.24, 2.99] | 0.74 | ||
| Plasma FT4, pmol/L | ||||||
| 2.5th percentile [95% CI] | 10.3 [10.1, 10.6] | 10.5 [10.3, 10.7] | 10.5 [10.2, 10.7] | 0.47 | ||
| 97.5th percentile [95% CI] | 16.1 [15.1, 17.0] | 15.4 [14.6, 16.3] | 15.4 [14.3, 16.4] | 0.35 | ||
| Plasma FT3, pmol/L | ||||||
| 2.5th percentile [95% CI] | 4.06 [3.93, 4.19] | 4.07 [3.95, 4.19] | 4.08 [3.94, 4.22] | 0.94 | ||
| 97.5th percentile [95% CI] | 6.03 [5.82, 6.24] | 5.88 [5.71, 6,06] | 5.90 [5.70, 6.11] | 0.30 | ||
Data from adjusted models: patients with TPOAb positive (TPOAb >4.11 IU/mL) and current users of thyroid medication or thyroid disrupting medication, and women who have undergone in vitro fertilization were excluded.
Values are from quantile regression and adjusted for maternal age, prepregnancy BMI, gestational age at sampling, urinary creatinine (when UIC∼Cr is the exposure), and energy intake (when iodine from food is the exposure). Results from crude models are reported in Supplementary Table S2.
a
p-Value from quantile regression.