Hair Loss

Why men lose hair: pattern loss vs. shedding

Most male hair loss is androgenetic alopecia — male pattern baldness. It's driven by an inherited sensitivity of scalp hair follicles to dihydrotestosterone (DHT), a hormone converted from testosterone. In sensitive follicles, DHT gradually shrinks (miniaturizes) each hair over successive growth cycles until the follicle produces only thin, short, barely visible hairs. That's why pattern loss is slow and follows a recognizable shape — a receding hairline at the temples, thinning at the crown, or both — and why it's common: around half of men show some degree of it by age 50.

Not all hair loss is pattern loss, though, and the difference matters because the fixes are different. Telogen effluvium is diffuse shedding across the whole scalp, typically triggered two to three months after a physical or physiological stressor — a high fever, surgery, a significant illness, a crash diet, certain medications — and thyroid disorders (both over- and underactive) are a recognized cause that usually reverses once thyroid levels are corrected ^[1]. Iron deficiency is frequently blamed too, though the clinical evidence for that link is more contested. The practical point: sudden, all-over shedding is worth a doctor visit and basic blood work before you buy anything for "male pattern baldness," because it may not be pattern baldness at all.

Sources: [1] Asghar et al., Cureus (2020) — Telogen Effluvium: A Review of the Literature

Finasteride: the strongest evidence — and real trade-offs

Finasteride (1 mg/day orally) blocks the enzyme that converts testosterone to DHT, lowering scalp DHT and slowing the miniaturization process at its source. Its evidence base is unusually strong for a men's health treatment. In the two pivotal one-year randomized trials, more than 1,500 men aged 18 to 41 with pattern hair loss took either finasteride or a placebo; over a thousand of them continued into a blinded second year. Men on finasteride had measurably more hair than men on placebo at both one and two years — while the placebo group kept losing hair, which is the part people tend to underweight ^[1]. For many men, the most realistic goal of finasteride is stopping further loss, with some regrowth as a bonus rather than the headline.

The trade-offs are real and worth taking seriously. A small percentage of men in trials reported sexual side effects such as reduced libido or erectile difficulty, usually reversible on stopping. Separately, there are reports of persistent sexual, mood, and cognitive symptoms after stopping, which remain debated. In 2022, following a citizen petition, the US FDA required suicidal ideation and behavior to be added to the adverse reactions listed on the Propecia label — while also stating that the available evidence did not establish that finasteride causes these problems ^[2]. The honest summary: for most users finasteride is well tolerated, but it is a prescription drug with an uncommon but real side-effect profile — exactly why it should be started with a doctor who knows your history, including any history of depression, rather than ordered casually.

Sources: [1] Kaufman et al., Finasteride Male Pattern Hair Loss Study Group, J Am Acad Dermatol (1998) — Finasteride in the treatment of men with androgenetic alopecia, [2] US FDA response to citizen petition FDA-2017-P-5787 on finasteride (Propecia) labeling (2022)

Minoxidil: topical, and the rise of low-dose oral

Minoxidil works differently — it doesn't touch DHT. Its exact mechanism isn't fully understood, but it appears to lengthen the growth phase of the hair cycle and enlarge shrinking follicles. In a 48-week randomized, placebo-controlled trial of nearly 400 men, 5% topical minoxidil produced substantially more regrowth than 2% minoxidil or placebo — about 45% more regrowth than the 2% solution — and men on 5% responded sooner. The main downside was more scalp itching and irritation with the stronger formula ^[1].

Low-dose oral minoxidil — the same drug in pill form at a fraction of the dose historically used for blood pressure — has become a popular off-label option, partly because a daily tablet is easier to stick with than twice-daily scalp application. The evidence is promising but still younger and thinner than for finasteride or topical minoxidil. A 2022 systematic review with meta-regression found that higher daily doses were associated with greater gains in hair density and thickness after six months — but also with more unwanted body-hair growth (hypertrichosis) and more cardiovascular side effects, such as a fast heart rate or fluid retention ^[2]. That dose-for-side-effect trade-off is exactly why oral minoxidil is a prescribing decision, not a supplement-aisle one.

Sources: [1] Olsen et al., J Am Acad Dermatol (2002) — 5% vs 2% topical minoxidil and placebo in men with androgenetic alopecia, [2] Gupta et al., Skin Appendage Disorders (2022) — Dose-dependent association between low-dose oral minoxidil and efficacy for androgenetic alopecia (systematic review with meta-regression)

Microneedling, supplements, and what the hype skips

Microneedling — rolling or stamping fine needles into the scalp to create controlled micro-injuries — gets a lot of attention, and the early data is genuinely interesting. In a 12-week randomized pilot study of 100 people, adding weekly microneedling to 5% minoxidil produced a much larger increase in hair count than minoxidil alone ^[1]. But it was a small, short study where patients knew which treatment they received, so it supports microneedling as a possible add-on to a proven treatment — not as a replacement for one.

Supplements are where the gap between marketing and evidence is widest. Biotin is the most common "hair vitamin," yet a review of the published cases found that every person who improved on biotin had an underlying condition or deficiency affecting hair growth — there's no good evidence it helps men with normal biotin levels ^[2]. (High-dose biotin can also distort some blood test results, including certain thyroid and heart tests, so tell your doctor if you take it.) Saw palmetto has weak DHT-blocking activity in some studies but nowhere near the effect of finasteride. Correcting a real deficiency — iron, vitamin D, or otherwise — is worth doing for its own sake, but it isn't a treatment for pattern baldness.

Sources: [1] Dhurat et al., Int J Trichology (2013) — A randomized evaluator-blinded study of microneedling in androgenetic alopecia (pilot study), [2] Patel, Swink & Castelo-Soccio, Skin Appendage Disorders (2017) — A Review of the Use of Biotin for Hair Loss

Can you actually reverse hair loss?

Partly — and the earlier you start, the more realistic it is. Treatments work on follicles that are shrinking but still alive; they can thicken miniaturized hairs and slow or halt further loss, but they can't revive follicles that have been inactive for many years. That's why the most consistent piece of advice in this field is to act early rather than wait until loss is advanced, and why expectations matter: "keeping what you have, plus some regrowth" is a good outcome, not a failure.

Patience is the other non-negotiable. Hair grows slowly and cycles over months, so any treatment needs roughly 3–6 months before you can judge it, and up to a year to see its full effect. Some men notice extra shedding in the first weeks of minoxidil, commonly attributed to follicles cycling into a new growth phase. Taking photos in the same lighting every three months is a more reliable way to track progress than the mirror. And because these treatments only work while you use them, stopping usually means the underlying pattern resumes. For men with advanced loss or who prefer not to take medication, hair transplant surgery is another established option, though transplanted areas still benefit from medical treatment to protect the surrounding native hair.

What this actually means for you

None of this is medical advice, and the disclaimer on this page applies to everything above. But if you're trying to cut through the noise: first, figure out what kind of hair loss you have — pattern loss and all-over shedding have different causes and different fixes, and a doctor or dermatologist can help tell them apart. If it's pattern loss, the treatments with the strongest evidence are still finasteride and minoxidil, and they work best started early and used consistently. Oral minoxidil and microneedling are reasonable things to discuss with a doctor, with the understanding that their evidence is younger. And nearly every supplement promising to regrow hair is selling hope, not results, unless you have a real deficiency.

The pattern across all of it is familiar from the rest of men's health: the proven options are unglamorous, slow, and require a doctor for the prescription ones — and anything promising dramatic regrowth in weeks deserves extra skepticism.