17α-Hydroxyprogesterone (17α-OHP), or hydroxyprogesterone (OHP) (INN, BAN), also known as 17α-hydroxypregn-4-ene-3,20-dione, is an endogenous progestogen steroid hormone related to progesterone. It is also a chemical intermediate in the biosynthesis of many other endogenous steroids, including androgens, estrogens, glucocorticoids, and mineralocorticoids, as well as neurosteroids. Under the brand name Gestageno, 17α-OHP has been marketed for clinical use in Argentina. However, esters of 17α-OHP, including hydroxyprogesterone caproate, as well as hydroxyprogesterone acetate and hydroxyprogesterone heptanoate to a much lesser extent, have been used far more widely in comparison, and when "hydroxyprogesterone" is referenced from the standpoint of medical use, what is usually being referred to is actually, in general, hydroxyprogesterone caproate. 17α-OHP is also the parent compound of a class of progestins referred to as the 17α-hydroxyprogesterone derivatives. Among others, this class of drugs includes chlormadinone acetate, cyproterone acetate, hydroxyprogesterone caproate, medroxyprogesterone acetate, and megestrol acetate.