Pollutant Chemicals, Thyrotropin, and Thyroid Hormone in Infants

Abstract

ISEE-0440 Background and Objective: Infants are exposed to chemicals that might interfere with thyroid function, such as perchlorate, thiocyanate, and nitrate. There are no studies available with individual measures of these chemicals and thyroid function in infants. We examined whether urinary perchlorate, nitrate, or thiocyanate is associated with urinary thyroxine (T4) and thyroid stimulating hormone (TSH) in infants. Because background perchlorate exposure has been associated with changes in thyroid hormone levels in adults, we specifically examined whether perchlorate was associated with higher TSH in infants with low iodide and in infant girls, as was seen in US females over age 12 years. Methods: The study was conducted at the Children’s Hospital of Philadelphia, the Hospital of the University of Pennsylvania, and affiliated clinics, among 92 full term infants (47 males and 45 females) between birth and 1 year of age. We used data from the Study of Estrogen Activity and Development, which was a partly cross-sectional, partly longitudinal study designed to assess hormone levels of full term infants over the first 12 months of life. We analyzed urine samples collected in that study. Main Outcome Measures: Urinary perchlorate, thiocyanate, nitrate, iodide, TSH and T4, and blood TSH and T4. Results: In models with single chemical agents, infants with higher perchlorate had higher TSH and T4. In models with all three chemical agents, infants with low iodide and higher perchlorate had higher T4 and TSH; infants with higher urinary thiocyanate or higher urinary nitrate had higher urinary TSH and T4. Conclusions: The association of perchlorate exposure with increased urinary TSH in infants with low urinary iodide is consistent with previous findings in females aged 12 and older. Higher thiocyanate and nitrate exposure is also associated with higher urinary TSH in infants. (Supported in part by the intramural research program of NIH.)