Together with the alpha chain CGA constitutes follitropin, the follicle-stimulating hormone, and provides its biological specificity to the hormone heterodimer. Binds FSHR, a G protein-coupled receptor, on target cells to activate downstream signaling pathways. Follitropin is involved in follicle development and spermatogenesis in reproductive organs. Heterodimer. The active follitropin is a heterodimer composed of an alpha chain/CGA shared with other hormones and a unique beta chain/FSHB shown here. Efficient secretion requires dimerization with CGA. Belongs to the glycoprotein hormones subunit beta family.