Antiandrogens

Notes                                                                                                                                                                                                              

• Androgens can play a significant role in acne, alopecia, hirsutism, and hidradenitis suppurativa.

• Antiandrogens = drugs that block androgen receptors = spironolactone, cimetidine, medroxyprogesterone acetate; flutamide, cyproterone acetate. 

• Androgen inhibitors = drugs that block androgen synthesis = finasteride and dutasteride, ketoconazole; leuprolide, nafarelin

• Progestins and combined OCPs have both actions

• Androgens = testosterone, dihydrotestosterone (DHT), androstenedione, DHEA, DHEA-S

  • testosterone and androstenedione can be metabolized to DHT​

  • testosterone can only enter cells if it is unbound to SHBG; only 1-2% of testosterone is unbound

  • testosterone is not very biologically active in many tissues (including skin) until converted to DHT by 5-alpha reductase of which there are 2 types: I and II

  • 5-alpha reductase is found in the skin (I and II), liver (I >> II), adrenals (I), kidneys (I), prostate (II), epididymis (II), seminal vesicles (II)

    • Type I in sebaceous glands and dermal papilla of nongenital skin (including scalp)​

    • Type II in front and vertex scalp, beard

  • Cutaneous hyperandrogenism can happen in the absence of systemic hyperandrogenism as a result of local enzyme activity as well as androgen receptor levels​; therefore, testosterone (free and total) and DHEA-S levels are often normal when tested. 

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