Bone morphogenetic protein 15 is a protein that in humans is encoded by the BMP15 gene. It's mainly involved in folliculogenesis. The protein encoded by this gene is a member of the TGF-β superfamily. It is a paracrine signaling molecule involved in oocyte and follicular development. Using Northern blot analysis, BMP15 has been shown to be exclusively expressed in the ovaries. It is thought that this protein may be involved in oocyte maturation and follicular development as a homodimer or by forming heterodimers with a related protein, Gdf9. Promotion of growth and maturation of ovarian follicles, starting from the primary gonadotrophin-independent phases of folliculogenesis. Regulation of the sensitivity of granulosa cells to follicle-stimulating hormone (FSH) action, contributing to the determination of the number of eggs that are ovulated. Prevention of granulosa cell apoptosis. Promotion of developmental competence of oocytes. Defects in BMP15 are associated with primary ovarian insufficiency. BMP15may represent a biomarker of ovarian response to ovarian stimulation or oocyte quality.