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The Effects of Triclosan on Puberty and Thyroid Hormones in Male Winstar Rats.
Citation:
Zorrilla, L. M., E K. GIBSON, S C. JEFFAY, K M. CROFTON, W. R. Setzer, R L. COOPER, AND T E. STOKER. The Effects of Triclosan on Puberty and Thyroid Hormones in Male Winstar Rats. TOXICOLOGY SCIENCE 107(1):56-64, (2008).
Impact/Purpose:
Triclosan is an antibacterial and it is detected routinely in wastewater effluents, aquatic species, and human breast milk, urine and blood serum. In this study, peri-pubertal male rats were exposed to triclosan for 31-days and examined for effects on pubertal development and thyroid function. The triclosan exposure resulted in decreases in thyroxine (30 mg/kg and higher, NOEL 3 mg/kg), increased liver weights (100 mg/kg and higher) and an increase in the hepatic enzyme, 7-pentaoxyresorufin O-pentaylase (PROD, 300 mg/kg). Triclosan is currently up for re-registration and the effects of triclosan on thyroid hormones will be important for use by the Program Office (OPP).
Description:
Triclosan (5-chloro-2-(2,4-dichlorophenoxy)phenol) is a potent antibacterial and antifungal compound that is widely used in personal care products, plastics and fabrics. Recently triclosan has been shown to alter endocrine function in a variety of species. The purpose of this study was to determine effects of triclosan on pubertal development and thyroid hormone concentrations in the male rat. Weanling rats were exposed to 0, 3, 30, 100, 200 or 300 mg/kg of triclosan by oral gavage from postnatal day (PND) 23 to 53. Preputial separation (PPS) was examined beginning on PND 33. Rats were killed on PND 53 and organ and reproductive tissue weights were recorded and serum was collected for subsequent analysis. Triclosan did not affect growth or the onset of PPS during the 31 day exposure. Serum testosterone was significantly decreased at 200 mg/kg, however no effects were observed on androgen-dependent reproductive tissue weights. In addition, triclosan significantly decreased total serum thyroxine (T4) in a dose dependent manner at 30 mg/kg and higher (no observed effect level, NOEL, of 3 mg/kg). Triiodothyronine (T3) was significantly decreased only at 200 mg/kg, but thyroid stimulating hormone (TSH) was not statistically different at any dose. Liver weights were significantly increased at 100 mg/kg triclosan and above, which suggests that an induction of hepatic enzymes (7-pentaoxyresorufin O-pentaylase, PROD) that may have contributed to the altered T4 and T3 concentrations. This study demonstrates that triclosan is an endocrine disruptor following exposure in the juvenile male rat.