Follicular Stimulating Hormone (FSH) is a key reproductive hormone. It acts on primary follicles by binding to granulosa cells and acting to increase fluid secretion into the follicular cavities. This causes them to grow rapidly. Granulosa cells also respond by secreting increasing levels of estradiol into the circulation.
FSH, together with LH, prmotes estrogen production by the ovary. It also induces egg development.
In males, FSH induces sperm development.
FSH is essentially absent until puberty. It is regulated by GnRH release from the hypothalamus.