Effects of Thyroid Hormones on Bovine Granulosa and Thecal Cell Function In Vitro: Dependence on Insulin and Gonadotropins

The objective of this study was to evaluate the influence of thyroxine (T4) and triiodothryonine (T3) on steroid production by bovine granulosa and thecal cells. Granulosa and thecal cells were obtained from small (1 to 5 mm) and large (> or = 8 mm) follicles of cattle, respectively, and cultured for 4 d. We conducted six experiments to evaluate the effect of 2 d of exposure to various doses of T3 or T4. In insulin- or insulin plus FSH-treated granulosa cells of experiment 1, 30 and 100 ng/ml of T4 had no effect on aromatase activity or progesterone production. In experiment 2, in the presence of insulin and FSH, 1 and 3 ng/ml of T3 weakly (