Nandrolone decanoate, sold under the brand name Deca-Durabolin among others, is an androgen and anabolic steroid (AAS) medication which is used primarily in the treatment of anemias and wasting syndromes, as well as osteoporosis in menopausal women. It is given by injection into muscle or fat once every one to four weeks. Side effects of nandrolone decanoate may include symptoms of masculinization like acne, increased hair growth, voice changes, and increased sexual desire. The medication is a synthetic androgen and anabolic steroid and hence is an agonist of the androgen receptor (AR), the biological target of androgens like testosterone and dihydrotestosterone (DHT). It has strong anabolic effects and weak androgenic effects, which give it a mild side effect profile and make it especially suitable for use in women and children. Nandrolone decanoate is a nandrolone ester and a long-lasting prodrug of nandrolone in the body. Nandrolone decanoate was first described in 1960 and was introduced for medical use in 1962. It was the second nandrolone ester to be introduced, following nandrolone phenylpropionate (NPP) in 1959, and is one of the most widely used nandrolone esters. It is also one of the most widely used AAS worldwide. In addition to its medical use, nandrolone decanoate is used to improve physique and performance, and is said to be the most widely used AAS for such purposes.