<unk> is a naturally occurring androstane steroid and is also known by the chemical name androst-4-en-17β-ol-3-one. It has a double bond between the C4 and C5 positions (making it an androstene), a ketone group at the C3 position, and a hydroxyl (alcohol) group at the C17β position. Derivatives<unk> esters are substituted at the C17β position with a lipophilic fatty acid ester moiety of varying chain length. Major<unk> esters include<unk> cypionate,<unk> enanthate,<unk> propionate, and<unk> undecanoate. A C17β ether prodrug of<unk>  cloxotestosterone acetate, has also been marketed, although it is little known and is used very rarely or no longer. Another C17β ether prodrug of<unk>  silandrone, also exists but was never marketed, and is notable in that it is orally active. In addition to ester and ether prodrugs, androgen prohormones or precursors of<unk>  such as dehydroepiandrosterone (DHEA), androstenediol, and androstenedione, exist as well, and convert into<unk> to variable extents upon oral ingestion. Unlike<unk> ester and ether prodrugs however, these prohormones are only weakly androgenic/anabolic. All synthetic AAS are derivatives of<unk>  Prominent examples include nandrolone (19-nortestosterone), metandienone (17α-methyl-δ1-testosterone), and stanozolol (a 17α-alkylated derivative of DHT). Unlike<unk>  AAS that are 17α-alkylated, like metandienone and stanozolol, are orally active. This is due to steric hindrance of C17β-position metabolism during the first-pass through the liver. In contrast, most AAS that are not 17α-alkylated, like nandrolone, are not active orally, and must instead be administered via intramuscular injection. This is almost always in ester form; for instance, in the case of nandrolone, as nandrolone decanoate or nandrolone phenylpropionate.
Testosterone 
Counterregulatory hormone
Menotropin
Luteinizing hormone
Orexin
Adrenocortical hormone
Androgen
Adrenalone