Thyroid stimulating hormone inhibits rat granulosa cell steroidogenesis in primary culture.

It is not known why hypothyroidism predisposes the ovary to develop cystic follicles in hCG-treated rats. This study examined the effect of TSH on steroidogenesis in cultured granulosa cells. Granulosa cells were isolated from the ovaries of hCG-treated Long-Evans rats. Cells were cultured in medium with either 0 or 100NM: testosterone or 25(OH)cholesterol and treated with 0, 2.5, 10 or 20 ng/ml of TSH. TSH reduced 3ß-HSDI activity in these cells to 12% of control. Progesterone secretion decreased by 72% and estradiol secretion was non-detectable during the second day of treatment with 20 ng/ml of TSH. We conclude that TSH is capable of regulating the secretion of progesterone and estradiol by cultured granulosa cells.