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Effect of a peri-juvenile exposure to Triclosan on serum androgens and thyroid hormone in the male Wistar rat
Citation:
Zorrilla, L. M., R. L. COOPER, E. K. GIBSON, S. C. JEFFAY, AND T. E. STOKER. Effect of a peri-juvenile exposure to Triclosan on serum androgens and thyroid hormone in the male Wistar rat. Presented at Triangle Consortium of Reproductive Biology, Durham, NC, February 23, 2008.
Impact/Purpose:
Presentation to TCRB '08
Description:
Triclosan (5-chloro-2-(2,4-dichlorophenoxy)phenol) is a potent antibacterial and antifungal compound that is widely used in personal care products. Studies testing triclosan exposure in the bullfrog showed altered thyroid hormone homeostasis. More recently, triclosan has been suggested to have both androgenic and estrogenic activity in multiple in vitro assays. The purpose of this study was to assess the effects of triclosan on thyroid function in a mammalian species, and to determine effects on pubertal development in the male rat. Rats (10 per group) 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, a marker of pubertal development) was examined beginning on PND 33. Rats were necropsied on PND 53 and reproductive tissue weights were recorded. Serum was collected at necropsy for hormonal analysis of testosterone (T), androstenedione (A), luteinizing hormone (LH), thyroxin (T4) and triiodothyronine (T3). No effects of triclosan were observed on terminal body weight or the age of onset of PPS. However, mean serum T was significantly decreased at 200 (59%) and 300 (34%) mg/kg. Serum A was significantly decreased (82%) at 200 mg/kg. In this study, the no effect level (NOEL) for the effect on T and A was 100 mg/kg. No effects were observed in the reproductive tissue weights (testes, ventral prostate, epididymides, seminal vesicles or levator anibulbocavernosus muscle, LABC) on PND 53. In addition, triclosan significantly decreased serum T4 in a dose response manner at 30 mg/kg and higher (3 mg/kg, NOEL). T3 was also significantly decreased at 200 mg/kg (NOEL, 100 mg/kg). Mean liver weights were significantly increased at 100 mg/kg and higher, which may indicate an induction of hepatic enzymes and subsequent clearance of T4. Further studies are ongoing to determine whether the suppression of androgens is due to increased steroid clearance or a suppression of LH.