Androstenedione. Computer model of a molecule of the steroid hormone, dietary supplement and banned drug androstenedione. It is sold under the brand name Andro. This hormone is produced in the adrenal glands and is the precursor to the male and female sex hormones. It is used illegally by athletes seeking to enhance their sporting performances. The molecule's chemical formula is C19.H26.O2. Atoms (spheres) are colour-coded: carbon (grey), hydrogen (light blue), oxygen (orange).