Increased 5 alpha-reductase activity in idiopathic hirsutism

Area of Science:

• Endocrinology
• Dermatology
• Reproductive Medicine

Background:

• Hirsutism, characterized by excess male-pattern hair growth, is often linked to androgen excess.
• Idiopathic hirsutism (IH) and polycystic ovary syndrome (PCOS) are common causes, but the underlying mechanisms, particularly skin's role, require further elucidation.

Purpose of the Study:

• To investigate the activity of 5 alpha-reductase (5α-RA) in genital skin.
• To determine if elevated androgens influence 5α-RA in women with IH and PCOS.
• To explore the relationship between 5α-RA, serum androgen levels, and hirsutism severity.

Main Methods:

• In vitro measurement of 5α-RA in genital skin samples from women with IH, PCOS, and controls.
• Incubation of skin with radiolabeled testosterone (T) to quantify conversion to dihydrotestosterone (DHT) and 5α-androstane 3α-17β-estradiol (3α-diol).
• Correlation analysis between 5α-RA, serum androgen levels, and Ferriman-Gallwey scores.

Main Results:

• Women with IH and PCOS exhibited significantly higher conversion ratios (CR) of T to DHT and T to 3α-diol compared to controls.
• Serum androgen levels showed no correlation with 5α-RA.
• The CR of T to DHT positively correlated with hirsutism severity (Ferriman-Gallwey score).

Conclusions:

• Increased 5α-RA in genital skin is a key feature in both IH and PCOS.
• The elevated 5α-RA in IH appears to be an intrinsic abnormality, independent of systemic androgen levels.
• Hirsutism in IH may be explained by enhanced peripheral androgen metabolism in the skin, challenging the term 'idiopathic'.