ABSTRACT
While it has long been known that first generation sulfonylureas have goitrogenic effects, knowledge about the effects of second generation sulfonylureas on the thyroid is insufficient. In this study, we aimed to investigate the effects of second generation sulfonylureas on the thyroid. Twenty four (15 females and 9 males, age 51.9 ± 2.1 years) diabetic patients were studied. They were treated with gliclazide ranging from 80 mg to 320 mg daily. Thyroid volume were calculated by thyroid ultrasound, 2-hour and 24-hour RAIU and thyroid function tests (FT 3, FT4, TSH, TU, FTI) were evaluated before and four months after treatment. Thyroid volume was found to be 17.0 ±1.3 ml before sulfonylurea treatment and 18.3 ±1.4 ml after treatment and the increase was statistically significant (P< 0.01**). 2-hour RAIU was found to be 20.0 ± 2.4 % before and 16.0 ± 1,5 % after treatment. 24- hour RAIU was found to be 36.9 ± 3.3 % before and 30.2 ± 2.4 % after treatment. The decrease in the 24-hour RAIU was statistically significant (P< 0.05*). No changes were observed for thyroid function tests. These results suggest that second generation sulfonylureas may have a goitrogenic effect, so it may be useful to investigate the effects of second generation sulfonylureas on the thyroid with more extensive studies.