Inhibins are heterodimeric glycoproteins that selectively suppress the secretion of pituitary follicle stimulating hormone (FSH). Inhibins are predominantly secreted by granulosa cells of the ovary and Sertoli cells in the testis. Based on the current understanding of inhibin structure, an alpha subunit dimerizes with either a beta A or beta B subunit to form inhibin A and B, respectively. Inhibin Alpha is immunoreactive in follicular granulosa cells, theca interna, testicular Sertoli and Leydig cells, and luteinized stromal-thecal and hilar cells within the gonads, visually localized to the cytoplasm of target cells.

Inhibin Alpha is an established marker for ovarian sex cord stromal tumors and has been one of the commonly used markers in gynecologic pathology. The antibody stains the majority of tumor cells in granulosa cell tumors, Sertoli cell tumors, Sertoli-Leydig cell tumors, Leydig cell tumors, steroid cell tumors, sex cord tumors, and gynandroblastomas.