Why do we lose hair?
Scalp hair grows in repeating cycles of anagen (growth) → catagen (regression) → telogen (rest). In androgenetic alopecia (AGA) the anagen phase shortens and follicles miniaturise under the influence of dihydrotestosterone (DHT), produced from testosterone by 5-α-reductase. Genetic studies show that polymorphisms in the androgen-receptor (AR) gene on the X-chromosome, as well as other risk loci (e.g., EDA2R), increase follicular sensitivity to DHT.
How big is the problem?
- Prevalence. Around 30 % of White men are affected by age 30, 50 % by 50, and 80 % by 70; comparable age-adjusted figures are reported for many Asian and Middle-Eastern populations.
- Psychosocial burden. Systematic reviews link moderate-to-severe AGA with higher rates of anxiety, depression and diminished quality of life; early onset (< 20 y) amplifies distress. (pmc.ncbi.nlm.nih.gov, jamanetwork.com)
Classification & differential diagnosis
| Condition | Typical clues | Key distinctions |
|---|---|---|
| Androgenetic alopecia | Gradual recession at temples / vertex, miniaturised hairs | Responds to anti-androgen & vasodilator therapy |
| Telogen effluvium | Sudden diffuse shedding 2–3 m after trigger | Usually self-limiting; trichogram shows > 20 % telogen roots |
| Alopecia areata | Smooth “coin-shaped” patches | Auto-immune; responds to corticosteroids / JAK inhibitors |
Evidence-based therapy for AGA (updated 2024-2025)
| Treatment | Mode of action | Latest evidence |
|---|---|---|
| Finasteride 1 mg po | 5-α-reductase-II block → ↓ DHT ≈ 70 % | 10 000-patient cohort found no increase in mood disorders over 12 m (JAAD, 2025, DOI 10.1016/j.jaad.2025.03.068) (pubmed.ncbi.nlm.nih.gov) |
| Topical finasteride 0.1 % + minoxidil 5 % | Local DHT suppression + K-ATP-channel vasodilation | 12-week RCT: + hair density & diameter vs. minoxidil alone; comparable safety (pubmed.ncbi.nlm.nih.gov) |
| Minoxidil 5 % topical | ↑ follicular blood flow, prolongs anagen | Corner-stone of therapy; long-term studies show 40-50 % slowing of progression |
| Low-dose oral minoxidil (LDOM, 0.25–5 mg/day) | Systemic vasodilator in micro-dose | 2024 systematic review: ≥ 70 % patients gained terminal hairs with rare hypotension (PROSPERO CRD42024581183) (frontiersin.org, pubmed.ncbi.nlm.nih.gov) |
| Finasteride 1 mg + oral minoxidil (2.5 mg) combo | Dual DHT block + vascular support | 12-m real-world study (n = 502) showed 92 % stabilisation/improvement in Norwood V-VI males (pmc.ncbi.nlm.nih.gov) |
Safety note: The 2025 cohort analysis above found no excess risk of depression or anxiety with finasteride; for LDOM the main monitoring parameters are blood pressure and heart rate.
First-visit algorithm for clinicians
- Digital trichoscopy → quantify miniaturisation ratio.
- Laboratory screen → thyroid panel, ferritin, vitamin D.
- Start baseline therapy
- Men: finasteride ± topical or oral minoxidil.
- Premenopausal women: topical/LDOM minoxidil; consider spironolactone.
- Follow-up at 6 m → global photographs; if sub-optimal, add LDOM, microneedling or low-level-laser.
- Long-term → annual PSA (men > 40 y on finasteride) and BP checks on LDOM.
Where is the science heading?
- AI-assisted trichoscopy now predicts “responders” to finasteride from scalp images commercial platforms showed > 80 % accuracy in pilot trials.
- siRNA therapy (SAMiRNA-AR68): weekly topical high-dose achieved + 1.3–1.9 hairs /cm²/month vs. placebo in a 60-patient RCT. (nature.com)
- Exosome injections, JAK inhibitors and cellular re-programming are in early human studies for drug-refractory cases.
Key take-aways
- Hair loss is multifactorial but largely modifiable earlier intervention means higher reversibility.
- Finasteride and minoxidil remain the gold standard; evolving formulations (topical finasteride, LDOM) broaden their use.
- Personalised therapy dose, delivery route, and digital monitoring is the dominant trend moving into 2026.
Use this overview as the introductory article, and link each subsequent deep-dive section (topical combos, LDOM, safety, tech, future therapies) back to the evidence summarised here.
