Danazol (Danol - Winthrop) is a semisynthetic steroid, derived from 17-α-ethinyl testosterone (ethisterone) which inhibits pituitary gonadotropin secretion, probably by inhibiting both synthesis and release. It has no oestrogenic or progestational action but slight anabolic and androgenic activity, and used where suppression of the hypothalemicpituitary-gonadal axis is required without the direct stimulant effects of gonadal steroids. Conditions where this is desirable and where good results have been reported include precocious puberty and some cases of endometriosis, gynaecomastia and pubertal breast hypertrophy.