Table 3.
Regression coefficients between maternal log10 urine perchlorate concentrations and serum thyroid hormone concentrations.a
| Group | n | T4 [βb (95% CI)] | fT4 [βb (95% CI)] | Log10TSH [βb (95% CI)] |
|---|---|---|---|---|
| All subjects | 1,476 | –0.70 (–1.06, –0.34) | –0.053 (–0.092, –0.013) | 0.071 (0.008, 0.133) |
| Iodide | ||||
| < 100 μg/L | 452 | –0.57 (–1.20, 0.07) | –0.022 (–0.100, 0.056) | 0.034 (–0.081, 0.148) |
| 100–300 μg/L | 698 | –0.44 (–0.95, 0.08) | –0.031 (–0.067, 0.005) | 0.094 (0.002, 0.189) |
| > 300 μg/L | 326 | –1.77 (–2.73, –0.81) | –0.172 (–0.305, –0.039) | 0.089 (–0.058, 0.236) |
| Thiocyanate | ||||
| < 519 μg/L | 360 | –0.41 (–1.05, 0.24) | –0.034 (–0.074, 0.006) | 0.039 (–0.092, 0.170) |
| 519–1,620 μg/L | 741 | –0.74 (–1.27, –0.21) | –0.082 (–0.154, –0.010) | 0.086 (0.005, 0.166) |
| > 1,620 μg/L | 375 | –1.28 (–2.04, –0.51) | –0.041 (–0.098, 0.016) | 0.115 (–0.021, 0.252) |
| Nitrate | ||||
| < 36.3 mg/L | 366 | –0.20 (–0.88, 0.48) | –0.040 (–0.133, 0.054) | 0.053 (–0.071, 0.178) |
| 36.3–81.9 mg/L | 737 | –0.72 (–1.32, –0.12) | –0.062 (–0.130, 0.006) | 0.093 (–0.014, 0.200) |
| > 81.9 mg/L | 369 | –1.04 (–1.70, –0.38) | –0.057 (–0.101, –0.013) | 0.099 (0.000, 0.199) |
| Ethnicity | ||||
| Hispanic | 1,035 | –0.78 (–1.21, –0.36) | –0.073 (–1.124, –0.023) | 0.037 (–0.032, 0.106) |
| Non-Hispanic | 441 | –0.59 (–1.27, 0.09) | –0.002 (–0.054, 0.050) | 0.184 (0.052, 0.317) |
| Sample collectionc | ||||
| ≤ 8 weeks apart | 470 | –1.05 (–1.73, –0.38) | –0.052 (–0.136, 0.033) | 0.001 (–0.121, 0.122) |
| > 8 weeks apart | 1,006 | –0.55 (–0.98, –0.13) | –0.050 (–0.092, –0.008) | 0.107 (0.036, 0.178) |
| Anti-thyroid antibodies | ||||
| Positived | 203 | –1.55 (–2.75, –0.34) | –0.093 (–0.159, –0.027) | 0.153 (–0.060, 0.365) |
| Negative | 1,273 | –0.52 (–0.89, –0.15) | –0.047 (–0.091, –0.002) | 0.060 (–0.004, 0.123) |
| Abbreviations: β, regression coefficient; fT4, free thyroxine; T4, total thyroxine; TSH, thyroid-stimulating hormone. aOnly includes participants with urinary creatinine concentrations between the 10th and 90th percentiles (i.e., 41–233 mg/dL). bAdjusted for urinary creatinine, maternal age, maternal education, ethnicity (Hispanic vs. non-Hispanic), gestational age at serum collection, and urinary thiocyanate. cWeeks between urine and serum sample collection. dIncludes participants with thyroperoxidase or thyroglobulin antibody concentrations above 9 and 4 IU/mL, respectively. | ||||