Pituitary follicular cells secrete both vascular endothelial growth factor and follistatin

Follistatin, a hormone which acts to suppress the release of follicle-stimulating hormone (FSH) by pituitary-derived gonadotrophs, has previously been identified only in the liquor folliculi of ovarian follicles. By microsequencing of fractions derived from conditioned medium, we show here that bovine pituitary-derived folliculo stellate cells are also capable of producing and secreting this hormone. These results suggest that folliculo stellate cells may serve as a source of follistatin within the pituitary itself and that the regulation of FSH release from the pituitary could therefore involve a paracrine mechanism.