Phthalates and thyroid function in preschool age children: Sex specific associations.

•In a study of inner-city mothers and their children, we measured metabolites of several phthalates in maternal prenatal urine and child urine collected at age 3.•We also measured serum free thyroxine and thyroid stimulating hormone in the children at age 3.•We found inverse and sex specific associations between specific phthalate metabolites measured in children at age 3 and free thyroxine.•The associations were limited to girls.•Maternal prenatal urine concentrations of MEHP, a metabolite of DEHP, were associated with increases in free thyroxine in children at age 3.•No associations were found between phthalate metabolites and thyroid stimulating hormone.