Abstract: OBJECTIVE: To investigate effects of long-term exposure to di-(2-ethylhexyl) phthalate (DEHP) on thyroid hormone levels in adult male rats. METHODS: Thirty-six healthy adult male Wistar rats were randomly divided into four groups according to body weight:control group and the 150,300 and 600 mg/kg DEHP exposure group. Rats were given normal food and water,but the rats in the exposed group were given DEHP by continuous gavage for 3 months. Before the rats were sacrificed,body masses of the rats were measured and the viscera ratio of each tissue was calculated. Urine iodine content,serum thyroid hormone content and serum TTR,TRH and TSAb levels were detected. One-way analysis of variance (ANOVA) was used to analyze the differences among the groups. SNK test was used for further multiple comparisons. RESULTS: After 3 months of exposure to DEHP,there was no significant change in body mass. Compared with the control group,there was no significant difference in the wet weight of thyroid and the ratio of viscera in each dose group. The ratios of liver viscera in the 150,300 and 600 mg/kg groups increased and showed a dose-effect relationship (P < 0.05). Urine iodine level of rats in the 600 mg/kg group was significantly decreased (P < 0.05). Serum FT4 level of rats in the 600 mg/kg group was decreased (P < 0.05). CONCLUSION: Exposure of rats to DEHP for 3 months had no significant effect on the body masses of rats. However,the exposure affected the function of thyroid and liver organs via inhibiting the synthesis,secretion and transport of TSH,and disrupting the thyroid hormone levels.

Key words: endocrine disrupting chemicals, DEHP, thyroid disease, thyroid hormone, male rats