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TRICLOSAN AND ENDOCRINE DISRUPTION: EVIDENCE FOR ALTERATIONS IN THYROID HORMONE HOMEOSTASIS.
PAUL, K. B., J. M. HEDGE, M. J. DEVITO, AND K. M. CROFTON. TRICLOSAN AND ENDOCRINE DISRUPTION: EVIDENCE FOR ALTERATIONS IN THYROID HORMONE HOMEOSTASIS. Presented at SETAC, Milwaukee, WI, November 11 - 15, 2007.
The current research tested the hypothesis that triclosan alters circulating concentrations of thyroxine.
Impact Statement: Triclosan (5-chloro-2-(2,4-dichlorophenoxy)phenol) is a chlorinated phenolic antibacterial compound found as an active ingredient in many personal care and household products. Recent studies suggest that triclosan may alter thyroid hormone (TH) homeostasis via activation of the human pregnane X receptor (PXR) and inhibition of diiodothyronine (T2) sulfotransferases. Additionally, exposure impacts TH-dependent developmental growth in anuran species. These effects, and structural similarity of triclosan to THs, suggest adverse impacts on thyroid homeostasis. The current research tested the hypothesis that triclosan alters circulating concentrations of thyroxine. The hypothesis was tested using a four-day oral triclosan exposure (0–1000 mg/kg/day) in weanling female Long Evans rats, followed by measurement of circulating levels of serum total thyroxine (T4). Dose-dependent decreases in total T4 were observed. The BMD and BMDL for the effects on T4 were 69.7 and 35.6 mg/kg/day, respectively. These data demonstrate that triclosan disrupts thyroid hormone homeostasis in rats.