Androstenedione is a steroid hormone that plays a crucial role in the production of both masculine and feminine sex hormones. This hormone is also known as A4 or delta-4-androstenedione. It is produced by the adrenal glands, testes, and ovaries. Androstenedione is classified as an androgen hormone, and elevated levels of this hormone in women can cause virilization. Some synonyms for androstenedione include AD, 4-androstenedione, 4-dione, androstene-dione, 4-AD, and andro. The steroid hormone is often used as an athletic supplement for building muscle mass, but its use has been banned by World Anti-Doping Agency (WADA).