Nandrolone Decanoate is a synthetic version of the naturally occurring hormone androsterone, which is produced by the human adrenal gland also acts as an androgen. A synthetic version of the hormone obviously named by precisely the same title, Deca-Durabolin, has been manufactured to provide a potent yet benign testosterone replacement treatment for those who cannot produce sufficient quantities of the hormone. These nutritional supplements are usually ingested orally or injected under the skin.