Danazol is used in the management of endometriosis. Its principal pharmacological action is:

• A Selective agonism at progesterone receptors in endometrial implants
• B Competitive antagonism at estrogen receptors throughout the reproductive tract
• C Suppression of pituitary gonadotropin secretion creating a hypoestrogenic state, with weak androgenic activity ✓
• D Irreversible inhibition of aromatase in peripheral tissues

Explanation

Danazol is an attenuated 17-alpha ethinyl testosterone derivative that suppresses the midcycle surge of LH and FSH, abolishing cyclical ovarian estrogen production and producing an atrophic environment for ectopic endometrium. It also binds androgen and progesterone receptors, explaining its androgenic adverse effects such as hirsutism, acne, voice deepening and weight gain. It is neither a pure estrogen receptor antagonist nor an aromatase inhibitor, which distinguishes it from tamoxifen and letrozole respectively.

Reference: Katzung Basic and Clinical Pharmacology, 15th ed.

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