Thyroid dysfunction exposure levels

Endocrine Effects. No biochemical evidence of thyroid dysfunction, as evaluated by serum levels of T4, triiodothyronine, and TSH, were reported in a group of 18 workers examined 17 years after an industrial accident during the manufacture of 2,4,5-T (Jennings et al. 1988). The small sample size, the fact that no measure of exposure was provided, and the long period of time between exposure and examination preclude any conclusion regarding possible effects of 2,3,7,8-TCDD. Zober et al. (1994) found a significant increase in the incidence of thyroid disease (no further details provided) 35 years after the BASF accident. An increased incidence of diabetes and subclinical decreases in thyroid function were found in Vietnam veterans who participated in operation Ranch Hand (USAF 1991). 

Neurological effects associated with phthalate exposure also have been reported in human studies. Although a mechanism of action has not been demonstrated, it is hypothesized that disruption of maternal thyroxine levels may contribute to the downstream clinical effects of thyroid dysfunction (Meeker et al. 2007). 

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