Danazol (danocrine) is a synthetic hormone approved by the U.S. Food and Drug Administration (FDA) to treat hereditary angioedema, fibrocystic breast disease, and endometriosis.

Endometriosis is a disease characterized by tissue resembling the endometrium (the tissue that lines the uterus) implanting in patches or lesions in other areas of the body. The endometrial lesions swell and shed with the menstrual cycle, but being located outside of the uterus, they cannot be expelled properly so lead to inflammation, and cause pain and infertility.

How Danazol works

Danazol is a testosterone derivative —  it has a chemical structure similar to the hormone testosterone. In males, testosterone controls the development of the physical characteristics such as hair and muscle growth, and deepening of the voice. Women also have testosterone but in very small quantities. The menstrual cycle is controlled by the hormones estrogen and progesterone, which are produced by the ovaries. Endometrial lesions also produce large quantities of estrogen, contributing to the symptoms of endometriosis.

Testosterone and testosterone derivatives such as Danazol decrease the amount of estrogen being produced by the ovaries and endometrial lesions, and bind to progesterone, preventing it from acting on its receptors.

Without estrogen, the endometrial lesions shrink and do not shed. Danazol induces artificial menopause so the patient stops ovulating, and menstruating.

Danazol in clinical trial for endometriosis

Three clinical trials (NCT03778359NCT00758953NCT01779232) have evaluated danazol in treating endometriosis, but no results have been published yet.

study published in the Cochrane Database of Systematic Reviews examined the records of randomized controlled trials in which Danazol (alone or as additive therapy) was compared with placebo or no therapy. Five trials met the selection criteria. The authors of the study concluded that treatment with Danazol (including treatment in addition to surgical therapy) was effective in relieving pain symptoms related to endometriosis when compared with a placebo. Laparoscopic scores for endometrial lesions were improved with Danazol treatment (including as an additive therapy) when compared with either placebo or no treatment. Side effects were more commonly reported in those patients receiving Danazol than for placebo.

Other information

Danazol may cause side effects including chest pain, rapid weight gain, upset stomach, diarrhea, and headache. Because Danazol is a testosterone derivative, it may cause the development of male physical traits such as hair growth, breast reduction, and deepening of the voice.


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