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 (By similarity). Follitropin is involved in follicle development and spermatogenesis in reproductive organs (PubMed:9020850, PubMed:11416011). 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. Mice lacking Fshb are viable (PubMed:9020850). Females are infertile displaying abnormal uterus and ovaries that lacked corpora lutea. The infertility is due to impaired follicle maturation which appears before antral follicle formation (PubMed:9020850). Males are fertile and spermatogenesis proceeds normaly. However, these mice display a reduced testes size and epididymal sperm count (PubMed:9020850, PubMed:11416011). The number of Sertoli cells is significantly reduced and their ability to support germ cell development is also affected (PubMed:11416011). Belongs to the glycoprotein hormones subunit beta family.