Gestational urinary bisphenol A and maternal and newborn thyroid hormone concentrations: the HOME Study

Abstract

Bisphenol A (BPA), an endocrine disruptor used in consumer products, may perturb thyroid function. Prenatal BPA exposure may have sex-specific effects on thyroid hormones (THs). Our objectives were to investigate whether maternal urinary BPA concentrations during pregnancy were associated with THs in maternal or cord serum, and whether these associations differed by newborn sex or maternal iodine status. We measured urinary BPA concentrations at 16 and 26 weeks gestation among pregnant women in the HOME Study (2003-2006, Cincinnati, Ohio). Thyroid stimulating hormone (TSH) and free and total thyroxine (T4) and triiodothyronine (T3) were measured in maternal serum at 16 weeks (n=181) and cord serum at delivery (n=249). Associations between BPA concentrations and maternal or cord serum TH levels were estimated by multivariable linear regression. Mean maternal urinary BPA was not associated with cord THs in all newborns, but a 10-fold increase in mean BPA was associated with lower cord TSH in girls (percent change=-36.0%; 95% confidence interval (CI): -58.4, -1.7%), but not boys (7.8%; 95% CI: -28.5, 62.7%; p-for-effect modification=0.09). We observed no significant associations between 16-week BPA and THs in maternal or cord serum, but 26-week maternal BPA was inversely associated with TSH in girls (-42.9%; 95% CI: -59.9, -18.5%), but not boys (7.6%; 95% CI: -17.3, 40.2%; p-for-effect modification=0.005) at birth. The inverse BPA-TSH relation among girls was stronger, but less precise, among iodine deficient versus sufficient mothers. Prenatal BPA exposure may reduce TSH among newborn girls, particularly when exposure occurs later in gestation.

Keywords: Bisphenol A; Endocrine disruptors; Epidemiology; Newborns; Pregnant women; Thyroid hormones; Thyroid stimulating hormone; Thyroxine; Triiodothyronine.

Figure 1

Percent change in thyroid stimulating hormone concentrations in cord serum (n=193) with 10-fold increase in maternal urinary BPA in the Health Outcomes and Measures of the Environment Study by newborn sex and iodine deficiency. Sufficient iodine was defined by maternal urinary iodine ≥150 µg/g creatinine (diamond marker) and deficient iodine as maternal urinary iodine <150 µg/g creatinine (circle marker). Percent change calculated as e^β −1×100, where β=coefficient from a multivariable linear regression model including adjustment for maternal age, race, education, alcohol consumption, smoking, parity, prenatal vitamin use, Log₁₀-polychlorinated biphenyl 153, delivery by Cesarean section, gestational week at delivery, newborn sex, iodine insufficiency, and product terms for bisphenol A by newborn sex, bisphenol A × iodine deficiency, newborn sex × iodine deficiency, and a bisphenol A × newborn sex × iodine deficiency. From left to right, the panels represent estimates from log₁₀-transformed creatinine-standardized bisphenol A in maternal urine at 16 weeks, 26 weeks, and the average of the log₁₀-transformed creatinine-standardized bisphenol A from maternal urine collected at the 16 and 26 week visits urine