inhibin, hormone secreted by the granulosa cells in the ovaries of women that acts primarily to inhibit the secretion of follicle-stimulating hormone by the anterior pituitary gland. Since the major action of follicle-stimulating hormone is to stimulate the formation and function of granulosa cells, the relationship between inhibin and follicle-stimulating hormone represents a typical negative feedback servomechanism. Small amounts of inhibin are produced by the Sertoli cells in the testes of men.