Does the thickness of hair strands decrease in men with androgenic alopecia? Can finasteride help to recover it?

Androgenic alopecia is often pictured as an extreme scenario: the total absence of hair. That picture can drive hasty decisions about treatments such as finasteride, before the process of the condition and how it evolves in each person is understood. However, androgenic alopecia is not a sudden event, but a progressive process where hair is not only lost in quantity, but also changes in thickness and quality before disappearing completely.

Understanding these changes helps in making informed decisions about the available treatments. Not all people experience the same progression or respond equally to medication. Finasteride is a prescription-only medicine, so it is worth knowing how androgenic alopecia affects hair, and what the trials do and do not show about the drug's effect on hair thickness, before discussing it with a doctor.

What is androgenic alopecia and how does it affect hair?

Androgenic alopecia is a genetic condition that affects both men and women, characterized by progressive hair loss in specific patterns. This condition is mainly due to the action of dihydrotestosterone (DHT), an androgen derived from testosterone. DHT binds to the receptors of susceptible hair follicles, causing their gradual miniaturization. This process reduces the size and functionality of the follicles, resulting in finer and shorter hair, and eventually, the disappearance of the affected follicle.

What are the physical effects of androgenic alopecia?

In addition to the reduction in the amount of hair, androgenic alopecia causes a progressive miniaturization of the hair follicles. This process implies that the affected follicles produce thinner and more fragile hairs. Over time, these follicles may stop producing hair altogether, leading to bald patches. Miniaturization is due to the action of DHT, which shortens the anagen (growth) phase of the hair cycle and prolongs the catagen (transition) and telogen (resting) phases, resulting in lower hair density and smaller diameter hairs.

Yes, but what is a hair follicle?

The hair follicle is the structure in the skin responsible for hair production. Each follicle acts as a "factory" that creates and regenerates hair in a cyclical manner. In people with androgenic alopecia, hair follicles gradually miniaturize, resulting in thinner, weaker hair. It is through this process that finasteride attempts to intervene, reducing the action of the hormone responsible for miniaturization (DHT) and promoting the production of thicker, healthier hair.

How does hair thinning manifest in men with androgenic alopecia?

Hair thinning in men with androgenic alopecia initially manifests as a progressive thinning of the hair strands, especially in the frontal and upper areas of the scalp. This thinning is due to the miniaturization of the hair follicles, where the follicles become smaller and produce finer, weaker hairs. Over time, this process can lead to the appearance of thinner, less dense hair. In advanced stages, a noticeable recession of the hairline and more extensive bald areas may be observed.

How does finasteride help with hair thickness?

Finasteride is a specific inhibitor of the enzyme 5-alpha-reductase type II, responsible for the conversion of testosterone into DHT. By reducing DHT levels, finasteride decreases its negative impact on hair follicles, slowing down the miniaturization process and allowing the follicles to produce thicker and stronger hair. This effect contributes to improving hair density and thickness in men with androgenic alopecia.

Studies confirming finasteride improves hair thickness

The pivotal evidence is the Finasteride Male Pattern Hair Loss Study Group trials reported by Kaufman and colleagues ^[1]. Two one-year randomised, double-blind, placebo-controlled trials enrolled 1,553 men aged 18 to 41 with male pattern hair loss on finasteride 1 mg/day or placebo, and 1,215 of them continued into blinded extension studies for a second year.

What the trials measured was hair count, in a one-inch diameter circle of balding vertex scalp with a baseline of 876 hairs. Finasteride produced increases of 107 hairs at one year and 138 hairs at two years relative to placebo (p < 0.001), while the placebo group lost hair progressively. Patient self-assessment, investigator assessment and a blinded expert panel's review of photographs all recorded improvement at one and two years. The authors described adverse effects as minimal.

That is a density and appearance result, not a thickness result. The trials did not report the diameter of individual hair shafts, and they ran for two years, so what happens beyond that is not covered by this evidence.

So the honest answer to the headline question is a qualified one. The pivotal trials show finasteride increasing hair counts and improving the assessed appearance of the hair; they do not report whether the individual strands got thicker. Because miniaturization is what makes strands thin in the first place, and finasteride acts on the hormone driving it, slowing miniaturization would be expected to affect calibre as well as count — but that is a mechanistic expectation, not a measured finding, and it is not what these trials tested. Studies that measure hair shaft diameter directly are what would settle it.

User experiences

Community users commonly report that finasteride helps maintain and increase hair thickness, especially alongside minoxidil and microneedling, and that shedding settles within a few months before regrowth appears. One long-term poster who began thinning at 22 described maintaining thick hair into his 40s on a consistent finasteride, minoxidil and ketoconazole routine over two decades ^[2]. Another, using topical finasteride with minoxidil, reported noticeable thickening in the crown at around nine months ^[3].

These are self-reported, unverified accounts from individuals, often on more than one treatment at once, and there is no way to separate the contribution of each. Results vary widely, and posts describing no benefit are less likely to be written. Read them as experience, not evidence.

Before you consider finasteride

Finasteride is a prescription-only medicine. Talk to a doctor or pharmacist before starting, stopping or combining it, and tell your prescriber if you develop sexual, mood or cognitive symptoms rather than adjusting the dose yourself.

Finasteride is contraindicated in pregnancy: it can cause abnormal development of the external genitals in a male fetus. Women who are or may become pregnant must not take finasteride and must not handle crushed or broken tablets.

Sources

Universidad Nacional de Rosario. Estudio sobre la alopecia y su tratamiento en medicina familiar. Rephip. https://rephip.unr.edu.ar/server/api/core/bitstreams/b1a52cc1-af6a-4b0e-8828-eeb390d34a1a/content

Sociedad Chilena de Dermatología. Guía sobre el diagnóstico y tratamiento de la alopecia androgenética. Revista Chilena de Dermatología, 31(1), 21-27. https://www.sochiderm.org/web/revista/31_1/21.pdf

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1. Kaufman, K. D., Olsen, E. A., Whiting, D., Savin, R., DeVillez, R., Bergfeld, W., Price, V. H., Van Neste, D., Roberts, J. L., Hordinsky, M., Shapiro, J., Binkowitz, B., & Gormley, G. J. (1998). Finasteride in the treatment of men with androgenetic alopecia. Finasteride Male Pattern Hair Loss Study Group. Journal of the American Academy of Dermatology, 39(4 Pt 1), 578-589. (PubMed 9777765) ↩︎

2. Reddit. (2023, June 8). I started rapidly diffuse thinning at 22, I'm 42 now. r/tressless. https://reddit.com/r/tressless/comments/fcae0j/i_started_rapidly_diffuse_thinning_at_22_im_42/ ↩︎

3. Reddit. (2023, July 10). About 9 months on topical finmin. r/tressless. https://reddit.com/r/tressless/comments/ohl9ef/about_9_months_on_topical_finmin/ ↩︎