Dexamethasone increases follicle-stimulating hormone secretion via suppression of inhibin in rats.

In the present study, the effects of dexamethasone on follicle-stimulating hormone (FSH) secretion in immature female rats were investigated. Dexamethasone increased the selective secretion of FSH and decreased plasma concentrations of inhibin in immature female rats. The effects of dexamethasone on FSH secretion were not confirmed in rats treated with ovariectomy or immunoneutralization against inhibin. In addition to the direct effect of dexamethasone on FSH synthesis in gonadotrophs, the present study has clearly demonstrated that the increased level of FSH in dexamethasone-treated rats is mediated by suppression of ovarian function, especially by the inhibition of inhibin secretion.