The TGFbeta superfamily is composed of numerous growth and differentiation factors, including transforming growth factor beta (TGFbeta) 1, 2 and 3; growth/differentiation factor (GDF) 1 through 8; Mullerian inhibiting substance (MIS); bone morphogenic protein (BMP) 2 through 8; glial cell line-derived neurotrophic factor (GDNF); Inhibins (alpha, beta-A, beta-B and beta-C), Lefty and Nodal. Members of the TGFbeta superfamily are involved in embryonic development and adult tissue homeostasis. Inhibins and activins inhibit and activate, respectively, the secretion of follitropin by the pituitary gland. Inhibins and activins are involved in regulating a number of 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. Activins oppose the funtions of Inhibins. Inhibins are predominantly expressed in liver, uterus and ovary tissue. Inhibin A, a dimer of alpha and beta-A, and Inhibin B, a dimer of alpha and beta-B, have been shown to inhibit the secretion of follicle stimulating hormone. Inhibin beta-C forms a homodimer and its expression is predominant in adult liver.