Male androgenetic alopecia is not a cosmetic fatality. It is a biological process whose molecular mechanisms have been documented for over three decades. It affects approximately 50% of men before age 50 and up to 80% before age 80 (PubMed). What makes it particular is that the scientific literature offers a structured, reproducible, dose-dependent protocol. Four axes of intervention now have a sufficient level of evidence to be presented as a coherent foundation.
DHT and the miniaturization cascade
Circulating testosterone is converted to dihydrotestosterone (DHT) by the enzyme 5-alpha reductase, present in high concentration in scalp follicles. DHT binds to androgenic receptors in the hair follicle and triggers a progressive shortening of the anagen phase, the part of the hair cycle during which the hair actively grows. Each cycle produces a thinner, shorter, less pigmented hair. This is follicular miniaturization.
Finasteride inhibits type II 5-alpha reductase and reduces serum DHT by approximately 70%, sufficient to slow or halt miniaturization in the majority of men.
This process is not uniform. It follows a genetically determined pattern, mapped by the Norwood-Hamilton scale. The temporal zones and vertex are most sensitive to DHT. The occipital zone (back of the skull) is largely spared, which explains its use as a donor area in hair transplant surgery.
The critical point is this: once a follicle is completely miniaturized, regeneration becomes improbable. Early intervention is not a luxury. It is a biological constraint.
The four axes validated by the literature
Oral finasteride: enzymatic inhibition
Finasteride is a selective inhibitor of type II 5-alpha reductase. At a dosage of 1 mg/day, it reduces serum DHT by approximately 70% (PubMed). Phase III clinical trials demonstrated an increase in hair count and improvement in clinical appearance in 83% of participants after two years.
Without DHT inhibition, other interventions merely slow a process whose cause remains active. This is why finasteride constitutes the first axis of any structured protocol.
Sexual side effects (decreased libido, erectile dysfunction) affect 2 to 4% of users and are reversible upon discontinuation in the vast majority of cases. Medical supervision remains essential.
Topical minoxidil: vascular stimulation
Minoxidil (5% solution) acts through a distinct mechanism. It prolongs the active growth phase of the hair and accelerates the return of resting follicles into a new growth cycle (PubMed). Its action involves the opening of ion channels in vascular cells, which causes blood vessel dilation in the scalp and improves nutrient delivery to the follicles.
Application is twice daily. Initial results generally appear between 4 and 6 months. A shedding phenomenon (temporary accelerated hair loss) frequently occurs in the first few weeks. This is a positive signal: resting follicles are being forced into a new growth cycle.
Ketoconazole: the antifungal and local anti-androgenic axis
Ketoconazole shampoo (2% concentration) has shown effects on hair density and size comparable to those of 2% minoxidil in a clinical trial (PubMed). Its mechanism of action extends beyond the antifungal effect: it reduces local testosterone production on the scalp and decreases inflammation around the follicles.
Recommended use is 2 to 3 times per week, leaving the product in contact with the scalp for 3 to 5 minutes before rinsing. This is the least demanding axis of the protocol and the one with the most favorable safety profile.
Microneedling: mechanical activation of growth factors
Scalp microneedling (dermaroller or dermapen, 0.5 to 1.5 mm needles) triggers a controlled wound-healing response. This response activates the Wnt/beta-catenin pathway, a signaling cascade that instructs stem cells to regenerate the follicle. It also stimulates the release of growth factors (PDGF, VEGF) that promote vascularization and cell proliferation.
A randomized clinical trial demonstrated statistically significant superiority of the microneedling + minoxidil group compared to minoxidil alone (PubMed). The combined group showed a mean hair count increase of 91.4 versus 22.2 for minoxidil alone after 12 weeks.
Recommended frequency is one session per week. Sterilizing the device with alcohol before and after each use is mandatory.
Emerging axes: what is taking shape
Three molecules are progressively expanding the available arsenal, without replacing the four preceding axes.
Dutasteride inhibits both isoforms of 5-alpha reductase (I and II), blocking more than 90% of DHT (PubMed). Its half-life (the time required for the body to eliminate half the molecule) is 5 weeks, compared to 8 hours for finasteride. Side effects therefore persist longer after discontinuation. It remains prescribed outside its official indication for alopecia in most European countries and is intended for finasteride non-responders.
Low-dose oral minoxidil (0.625 to 2.5 mg/day) represents an alternative for patients in whom the topical form fails. The enzymatic conversion of minoxidil to its active form (minoxidil sulfate) occurs primarily in the liver, which explains why the oral route can prove more effective than the topical route in certain individuals. Blood pressure monitoring is imperative.
PP405 constitutes the most novel approach. It blocks a transporter located in mitochondria (the cell's energy powerhouses), which alters the metabolism of follicle stem cells and promotes their activation. Phase 2a results showed that 31% of participants exhibited a hair density increase greater than 20% after just 8 weeks (study). Phase 3 is expected.
What biology imposes as a conclusion
Androgenetic alopecia is not a domain where empiricism works. Supplements based on biotin, saw palmetto, or marine collagen, despite their popularity, do not have a level of evidence comparable to the four axes described above. Biotin has documented interest only in rare cases of confirmed deficiency, not in standard androgenetic alopecia.
The protocol that emerges from the literature follows a transparent logic: block the cause (DHT), stimulate growth (minoxidil), reduce local inflammation (ketoconazole), activate mechanical regeneration (microneedling). Four distinct, complementary, dosed, and documented mechanisms.
Ongoing research on PP405 and oral minoxidil forms suggests that this arsenal will continue to expand. But the foundation has remained the same for two decades. It is solid. And it is available.
Frequently asked questions
References
- Kaufman KD, Olsen EA, Whiting D, et al. Finasteride in the treatment of men with androgenetic alopecia. J Am Acad Dermatol. 1998;39(4 Pt 1):578-589 (PubMed).
- Olsen EA, Dunlap FE, Funicella T, et al. A randomized clinical trial of 5% topical minoxidil versus 2% topical minoxidil and placebo in the treatment of androgenetic alopecia in men. J Am Acad Dermatol. 2002;47(3):377-385 (PubMed).
- Hugo Perez BS. Ketocazole as an adjunct to finasteride in the treatment of androgenetic alopecia in men. Med Hypotheses. 2004;62(1):112-115 (PubMed).
- Dhurat R, Sukesh M, Avhad G, et al. A randomized evaluator blinded study of effect of microneedling in androgenetic alopecia. Int J Trichology. 2013;5(1):6-11 (PubMed).
- Olsen EA, Hordinsky M, Whiting D, et al. The importance of dual 5alpha-reductase inhibition in the treatment of male pattern hair loss: results of a randomized placebo-controlled study of dutasteride versus finasteride. J Am Acad Dermatol. 2006;55(6):1014-1023 (PubMed).
- A Study to Evaluate Safety and Efficacy of PP405 in Males With Androgenetic Alopecia. ClinicalTrials.gov. NCT06393452 (study).
