THYROID-STIMULATING HORMONE INHIBITS RAT GRANULOSA-CELL STEROIDOGENESIS IN PRIMARY CULTURE

It is not known why hypothyroidism predisposes the ovary to develop cy stic follicles in hCG-treated rats. This study examined the effect of TSH on steroidogenesis in cultured granulosa cells. Granulosa cells we re isolated from the ovaries of hCG-treated Long-Evans rats. Cells wer e cultured in medium with either 0 or 100 nM testosterone or 25(OH)cho lesterol and treated with 0, 2.5, 10 or 20 ng/ml of TSH. TSH reduced 3 beta-HSDI activity in these cells to 12% of control. Progesterone sec retion decreased by 72% and estradiol secretion was non-detectable dur ing the second day of treatment with 20 ng/ml of TSH. We conclude that TSH is capable of regulating the secretion of progesterone and estrad iol by cultured granulosa cells.