Danazol is a derivative of the synthetic steroid

Steroid

A steroid is a type of organic compound that contains a characteristic arrangement of four cycloalkane rings that are joined to each other. Examples of steroids include the dietary fat cholesterol, the sex hormones estradiol and testosterone, and the anti-inflammatory drug dexamethasone.The core...

 ethisterone

Ethisterone

Ethisterone is a progestogen hormone.The first orally active progestin, ethisterone , the 17α-ethynyl analog of testosterone, was synthesized in 1938 by Hans Herloff Inhoffen, Willy Logemann, Walter Hohlweg, and Arthur Serini at Schering AG in Berlin and marketed in Germany in 1939 as Proluton C...

, a modified testosterone

Testosterone

Testosterone is a steroid hormone from the androgen group and is found in mammals, reptiles, birds, and other vertebrates. In mammals, testosterone is primarily secreted in the testes of males and the ovaries of females, although small amounts are also secreted by the adrenal glands...

. Also known as 17alpha-ethinyl testosterone. Before becoming available as a generic drug

Generic drug

A generic drug is a drug defined as "a drug product that is comparable to brand/reference listed drug product in dosage form, strength, route of administration, quality and performance characteristics, and intended use." It has also been defined as a term referring to any drug marketed under its...

, Danazol was marketed as Danocrine in the United States. It was approved by the U.S. Food and Drug Administration

Food and Drug Administration

The Food and Drug Administration is an agency of the United States Department of Health and Human Services, one of the United States federal executive departments...

 (FDA) as the first drug to specifically treat endometriosis

Endometriosis

Endometriosis is a gynecological medical condition in which cells from the lining of the uterus appear and flourish outside the uterine cavity, most commonly on the ovaries. The uterine cavity is lined by endometrial cells, which are under the influence of female hormones...

 in the early 1970s. Although effective for endometriosis, its use is limited by its masculinizing side-effects.