Inhibins and activins inhibit and activate, respectively, the secretion of follitropin by the pituitary gland. Inhibins/activins are involved in regulating a number of diverse functions such as hypothalamic and pituitary hormone secretion, gonadal hormone secretion, germ cell development and maturation, erythroid differentiation, insulin secretion, nerve cell survival, embryonic axial development or bone growth, depending on their subunit composition. Inhibins appear to oppose the functions of activins. Inhibin deficient mice are viable but are acutely sensitive to development of gonadal sex-cord stromal tumors. Dimeric, linked by one or more disulfide bonds. Inhibin A is a dimer of alpha and beta-A. Inhibin B is a dimer of alpha and beta-B. Proteolytic processing yields a number of bioactive forms, consisting either solely of the mature alpha chain, of the most N-terminal propeptide linked through a disulfide bond to the mature alpha chain, or of the entire proprotein. Belongs to the TGF-beta family.