Nandrolone. Computer model of part of a molecule of the anabolic steroid drug nandrolone (formula C18H26O2). Atoms are colour-coded: carbon (green), oxygen (red) and hydrogen (gold). Nandrolone is used to help build muscle and bone, and has been used to treat osteoporosis (brittle bones) in post-menopausal women. It has also been illegally abused by athletes as it increases strength and stamina. Overuse of nandrolone may cause liver damage. It may also cause virilization (development of masculine characteristics) in women and infertility in men.