Urinary nitrate, thiocyanate, and perchlorate and serum thyroid endpoints based on NHANES 2001 to 2002

OBJECTIVE:: To determine, on the basis of iodide uptake inhibition (IUI), whether associations between urinary concentrations of IUI agents (perchlorate, nitrate, and thiocyanate), as total perchlorate equivalent concentration (PEC), and serum thyroid parameters suggest functional thyroid abnormalities. Additional thyroid hormone measures were released to augment the National Health and Examination Survey (NHANES) 2001 to 2002 data set, which we used in this study. METHODS:: Enhanced thyroid hormone measures released to augment the National Health and Examination Survey (NHANES) 2001-2002 data set were used in this study. Multiple regression was used to assess the relationships among total thyroxine (TT4), free thyroxine, total triiodothyronine (TT3), free triiodothyronine, and thyroid- stimulating hormone (TSH) and PEC. RESULTS:: PEC was weakly and negatively associated with TT4, but not with TSH, TT3, or free hormone. This association with TT4 appears to be dominated by nitrate and thiocyanate. CONCLUSION:: No evidence of functional thyroid abnormality (eg., low thyroid hormone coupled with high TSH) was seen with exposure to the combined IUI agents and enhanced estimates of thyroid function.