INHA, also known as Inhibin alpha, belongs to the TGF-beta family. Inhibins and activins inhibit and activate, respectively, the secretion of follitropin by the pituitary gland. The inhibin alpha subunit joins either the beta A or beta B subunit to form a pituitary FSH secretion inhibitor. Inhibin has been shown to regulate gonadal stromal cell proliferation negatively and to have tumour-suppressor activity. 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. Recombinant human INHA protein, fused to His-tag at N-terminus, was expressed in E.coli.