Androgens “stimulate and thicken hair growth in skin” while androgens “suppress growth and shrink hair follicles”.
One of the most effective treatments for Male and Female hair loss is the use of Low dose Oral Minoxidil. In a 1404 patient multi-center study the most common side effect, hirsutism (increased facial body hair) caused 1% of patients to discontinued LDOM. The treatment to reverse this side effect is the use of Spironolactone.
How can Spironolactone increase scalp hair and decrease facial and body hair?
Spironolactone can have opposite effects on facial versus scalp hair due to the different ways hair follicles in these regions respond to androgens (male hormones) like testosterone and DHT. This phenomenon is often called the "androgen paradox".
Spironolactone works primarily by inhibiting the effects of androgens in two main ways:
- Blocking androgen receptors: It binds to androgen receptors in hair follicles, preventing androgens like DHT from attaching and activating them.
- Reducing androgen production: It inhibits the production of androgens in the body.
This anti-androgen activity affects facial and scalp follicles differently, producing contrasting outcomes. The effect of Spironolactone blocks androgen stimulation, leading to finer hair and reduced growth while at the same time blocks androgen-induced miniaturization, leading to thicker hair.
Effect on facial hair
Spironolactone reduces unwanted facial hair growth (a condition called hirsutism) because facial hair follicles are stimulated and thickened by androgens. By blocking androgen receptors in the skin, spironolactone counteracts this effect, causing facial hair to grow more slowly, become finer, and be less noticeable. However, this effect can require a higher dose than the 25 mg specified in the query, with noticeable results typically occurring at dosages of 50–200 mg.
Effect on scalp hair
For individuals with female pattern hair loss (androgenetic alopecia), excessive androgen activity on the scalp has the opposite effect. Androgens cause the scalp hair follicles to shrink, shorten the growth cycle, and produce thinner, finer hair. By blocking androgen receptors on the scalp, spironolactone prevents this follicle miniaturization and helps reverse the hair thinning process, leading to thicker and healthier hair.
It is important to note that 25 mg is a low dose of spironolactone, often used to begin treatment. While some androgen-blocking effects may occur, this dosage is typically below the range shown to produce significant changes in facial hair. For treating hirsutism, doses of 50–200 mg are more common.