Intracrinology and the skin

Area of Science:

• Endocrinology
• Dermatology
• Biochemistry

Background:

• The skin contains androgen-sensitive components that convert dehydroepiandrosterone (DHEA) into dihydrotestosterone (DHT).
• Adrenal DHEA production decreases with age, impacting skin steroidogenesis, especially in post-menopausal women.
• DHEA's effects in the skin are predominantly androgenic, as evidenced by antiandrogen blocking of sebaceous gland stimulation.

Purpose of the Study:

• To elucidate the specific enzymes and pathways involved in DHEA conversion to active androgens in human skin.
• To investigate the differential effects of DHEA in various tissues, including skin, vagina, and endometrium.

Main Methods:

• RNase protection assays and immunocytochemistry were used to identify steroidogenic enzymes in human skin.
• In vivo and in vitro studies using animal models and human tissues were conducted to assess DHEA's effects.

Main Results:

• Human skin expresses type 1 3beta-hydroxysteroid dehydrogenase (3beta-HSD) converting DHEA to androstenedione, and type 5 17beta-HSD converting androstenedione to testosterone.
• Type 1 5alpha-reductase is responsible for converting testosterone to DHT in the skin.
• DHEA exhibits estrogenic effects in the vagina but does not affect the endometrial epithelium in experimental animals and post-menopausal women.

Conclusions:

• The skin possesses a complete enzymatic system for converting DHEA into potent androgens like DHT.
• DHEA's tissue-specific actions (androgenic in skin, estrogenic in vagina) highlight its complex role in hormone physiology.
• DHEA's lack of endometrial effects suggests its safety for hormone replacement therapy without necessitating progestins.