Allylestrenol (INN) (brand names Gestanon, Gestanin, Orageston, Turinal, Gestin, others), or allyloestrenol (BAN), also known as 17α-allylestr-4-en-17β-ol or as 3-deketo-17α-allyl-19-nortestosterone, is a synthetic steroid with progestational activity, that is used to prevent threatened miscarriage, recurrent pregnancy loss, and premature labor. Allylestrenol has also been studied as a treatment for benign prostatic hyperplasia in men, with encouraging results. Although it is less potent as a progestogen relative to many other 19-nortestosterone derivatives, allylestrenol is said to be virtually devoid of androgenic, estrogenic, or glucocorticoid activity, and hence, unlike virtually all other 19-nortestosterone derivatives, appears to be a pure progestogen with similar effects to those of progesterone. Allylestrenol is widely marketed throughout Europe, including Russia and many other European countries, and is also available in Japan, Hong Kong, India, Bangladesh, Indonesia, and much of Southeast Asia, though notably not in the United States or Canada.