Background: Treatment with antiepileptic drugs such as phenobarbital (PB), carbamazepine (CBZ) and sodium valproate (VPA) has a lot of complications and may affect the endocrine function. The aim of this study was to evaluate the effects of CBZ and VPA on thyroid function tests.

Materials and Methods: This descriptive cross-sectional study was conducted on 50 patients referred to Kashan Shahid-Beheshti hospital during 2010-2011. The patients were randomly divided into two treatment groups with CBZ (n=22) and VPA (n=28). Patients with thyroid, hepatic and renal disorders, pregnants and those who had taken levothyroxine and oral contraceptives were excluded from the study. Fasting blood samples were taken from all patients and T3, T4, FT4, TSH and rT3 uptake were measured before and after 2 months of treatment.

Results: Forty-four cases had tonic-clonic and 6 cases partial seizure. In the CBZ group, there was no change in the mean values of T3 and rT3 T4 level was decreased and TSH and FT4 levels were increased, but the differences were not statically significant. Moreover, T3 level was significantly increased in the VPA group (P=0.038).

Conclusion: According to the results of the study, the mean T3 level was significantly increased in the VPA group.