Can Testosterone Grow Hair or Cause Hair Loss?

Testosterone does both: it thickens body and facial hair while, in genetically susceptible follicles on the scalp, it accelerates hair loss. The same hormone produces opposite outcomes depending on where the follicle sits, a phenomenon researchers call the “androgen paradox.” The explanation involves not testosterone itself but its more potent derivative, dihydrotestosterone (DHT), and the wildly different ways follicles in various parts of your body are programmed to respond to it.

The Androgen Paradox

During puberty, rising androgen levels transform many of the fine, nearly invisible hairs on your body into thicker, darker ones. Your beard fills in, chest hair appears, and hair on your arms and legs becomes more prominent. At the same time, in people with the right genetic setup, those same androgens begin shrinking hair follicles on the scalp, eventually producing the thinning pattern most people recognize as male-pattern hair loss. This contradiction, where one hormone simultaneously grows and destroys hair, has puzzled researchers for decades.¹

The paradox is not about the hormone being different in different locations. It is about the follicles being different. Beard follicles and scalp follicles contain the same androgen receptors, but they are epigenetically programmed to interpret the androgen signal in opposite ways. Beard follicle cells respond to androgens by releasing growth-promoting signals, while balding scalp follicle cells respond to the same androgens by releasing growth-suppressing signals.² Some follicles, like those on your eyelashes, simply ignore androgens altogether.¹

Why DHT Matters More Than Testosterone

Testosterone circulating in your blood is not the primary driver of scalp hair loss. The real culprit is DHT, which is made from testosterone by an enzyme called 5-alpha reductase. DHT binds to androgen receptors far more strongly than testosterone does, and it is this amplified signal inside the follicle that triggers the miniaturization process. Androgenetic alopecia can be understood as a DHT-dependent process in which sensitive follicles progressively shrink over time.³

One of the strongest pieces of evidence for DHT’s central role comes from observations of men born with a genetic deficiency in 5-alpha reductase. These individuals produce testosterone normally but cannot convert much of it to DHT. They grow little to no beard hair, and they do not develop male-pattern baldness, even into old age.⁴ This natural experiment tells us something important: testosterone alone is not enough to cause scalp hair loss. You need the conversion step.

The type 2 form of the 5-alpha reductase enzyme is especially active in scalp hair follicles and plays a central role in local DHT production.³ Meanwhile, beard follicles also produce DHT but respond to it by growing rather than shrinking, which underscores that the enzyme activity alone does not determine the outcome. The follicle’s internal programming does.

What Happens Inside a Shrinking Follicle

When DHT binds to androgen receptors in a susceptible scalp follicle, the dermal papilla cells at the base of the follicle start producing a cocktail of growth-suppressing signals. Among the best-studied are TGF-beta (both the beta-1 and beta-2 forms) and a protein called DKK-1. These molecules tell the surrounding hair-producing cells to slow down and shrink.² The net effect is that each growth cycle produces a thinner, shorter hair until the follicle eventually produces only a barely visible wisp, if anything at all.

In beard follicles, the same androgen signal triggers production of a different molecule, IGF-1, which promotes cell growth and division. So the hardware is similar across the body, but the software running on it is fundamentally different. Beard cells get a “grow” command; balding scalp cells get a “shrink” command.²

Lab studies also show that androgen-dependent follicles (like those in the beard) contain more androgen receptors per cell than follicles from non-balding scalp areas.⁵ This higher receptor density may be part of why these follicles are so responsive to androgens in the first place.

Blood Supply Changes in Balding Scalp

The shrinking process is not just about growth signals going haywire. There is also a vascular component. In balding scalp, the tiny blood vessels that feed the dermal papilla actually regress. Transcriptome analysis has identified significant microvascular abnormalities in the dermal papilla of balding scalp compared to non-balding scalp, and this blood vessel regression appears to happen early in the miniaturization process.⁶ A follicle losing its blood supply is a follicle losing its ability to sustain a thick hair shaft.

Interestingly, blocking androgen activity in lab settings stimulates production of VEGF, a molecule that promotes blood vessel growth.⁷ This suggests that androgens in the scalp suppress not only hair cell growth but also the blood supply that hair cells depend on, compounding the damage.

How Testosterone Therapy Affects Hair

If you are receiving testosterone, whether for hormone replacement, gender-affirming care, or any other reason, the effects on hair are predictably mixed. Body and facial hair growth is one of the most consistent and well-documented effects. In a study of transgender men receiving testosterone, facial and body hair increased progressively, with the Ferriman-Gallwey score (a standard measure of body hair) rising from a median of 0.5 at baseline to 12 after one year. After long-term treatment, nearly all participants reached scores that would be considered significant body and facial hair growth.⁸ Testosterone also increases hair growth rate and skin oil production in people assigned female at birth.⁹

On the scalp, the picture is less rosy. A prospective study of men using anabolic androgenic steroids found that while only about 2% reported hair thinning at baseline, that number climbed to about 12% by the end of a cycle lasting roughly three and a half months. A small percentage also reported increased scalp hair growth, showing that individual responses vary.¹⁰ The expected effects of testosterone therapy for transgender men include increased facial and body hair, increased lean mass, voice deepening, and cessation of menstruation, but accelerated scalp hair loss is a recognized possibility for those with genetic susceptibility.¹¹

Female Pattern Hair Loss and Androgen Excess

Women can experience androgen-driven hair loss too, though the pattern differs. Instead of a receding hairline, women tend to develop diffuse thinning across the top of the scalp while keeping their frontal hairline.¹² Polycystic ovary syndrome (PCOS), a condition that often involves elevated androgen levels, is strongly associated with this type of hair loss. A pooled analysis found that roughly 28% of women with PCOS have female pattern hair loss.¹³

The irony for women with androgen excess is that the same hormonal imbalance causing hair thinning on their scalp often causes unwanted hair growth on the face, chest, and abdomen. This is the androgen paradox in action across a single person’s body: too much hair where you do not want it, not enough where you do.

Why Your Blood Testosterone Level Does Not Predict Balding

One of the most persistent misconceptions is that men with higher testosterone levels are more likely to go bald. The reality is more nuanced. A cross-sectional study of patients with androgenetic alopecia found no significant correlation between serum testosterone levels and the severity of hair loss, regardless of gender. The same study also found no association between severity and serum estradiol, DHEA-sulfate, or vitamin D levels. In women, there was a significant negative correlation between sex-hormone-binding globulin (SHBG) levels and hair loss severity, but no such link appeared in men.¹⁴

This makes sense when you understand the mechanism. What matters is not how much testosterone is floating in your blood but how efficiently your scalp follicles convert it to DHT, how many androgen receptors those follicles have, and what downstream signals those receptors trigger. Two men with identical testosterone levels can have dramatically different hair outcomes based on their local enzyme activity and follicular programming. The balding one is not “more manly”; his follicles are just wired differently.

Medications That Block the Testosterone-to-DHT Conversion

The most widely used drugs for androgenetic alopecia, finasteride and dutasteride, work by inhibiting 5-alpha reductase and reducing DHT levels. Finasteride at a 1 mg dose reduces scalp DHT by roughly 64% and serum DHT by about 71%.¹⁵ Clinical trials with finasteride have shown improvements in scalp hair growth associated with these DHT reductions, along with evidence that follicle miniaturization starts to reverse.¹⁶

Dutasteride inhibits both the type 1 and type 2 forms of 5-alpha reductase, whereas finasteride targets primarily type 2. In head-to-head studies, dutasteride reduced scalp and serum DHT in a dose-dependent fashion and raised testosterone levels (since less testosterone was being converted).¹⁷ A trial of topical dutasteride solutions found that lower concentrations avoided significant changes in serum hormones, suggesting a way to reduce scalp DHT locally without shifting the body’s overall hormonal balance.¹⁸

For women, spironolactone is often used as an antiandrogen treatment. It works differently, blocking DHT from binding to androgen receptors rather than preventing its creation. A meta-analysis found that overall, about 57% of women treated with spironolactone showed improvement in hair loss, with combined therapy (spironolactone plus another treatment) reaching about 66%.¹⁹

Topical Androgen Blockers on the Horizon

One of the limitations of oral antiandrogen therapy is that it affects androgen signaling everywhere in the body, which can produce side effects. Topical androgen receptor antagonists are an active area of drug development aimed at blocking DHT’s effects right at the follicle without systemic exposure. Clascoterone is one such compound that has been shown to work as a potent antiandrogen in dermal papilla cells, with selective topical activity.²⁰

An older experimental compound, RU58841, demonstrated strong hair-growth-promoting effects when applied topically to bald scalp in primate models, increasing hair density, thickness, and length with no detectable systemic effects.²¹ More recently, researchers have identified novel compounds with high skin exposure and low plasma exposure following topical application that showed potent hair-growth-promoting effects in mouse models without noticeable toxicity.²² The appeal of these agents is clear: shut off the balding signal at the scalp without affecting testosterone’s other functions throughout the body.

Non-Hormonal Factors That Make Things Worse

Androgens are the primary driver of androgenetic alopecia, but they do not act alone. Oxidative stress, the accumulation of damaging reactive molecules in tissues, appears to interact with genetic susceptibility and androgens to worsen follicle damage.²³ This helps explain why some people with identical hormonal profiles experience hair loss at different rates: environmental stressors, smoking, UV exposure, and even local inflammation can accelerate what androgens started.

Inflammation also plays a role in a more structural way. Perifollicular fibrosis, the buildup of scar-like tissue around miniaturizing follicles, is a recognized feature of androgenetic alopecia. This fibrotic process disrupts the communication between the dermal papilla and the hair-producing cells above it, further impairing the follicle’s ability to regenerate.²⁴ This is relevant to the question of reversibility: early-stage miniaturization can often be partially reversed with treatment, but once fibrosis sets in around a follicle, recovery becomes much harder.

The Enzyme Distribution That Shapes Regional Differences

The two forms of 5-alpha reductase are not evenly distributed across the body, and their distribution helps explain some of the regional differences in hair response. Type 1 is concentrated in sebaceous glands, especially those in facial skin and scalp, where its activity is substantially higher than in non-acne-prone areas.²⁵ Different follicle types also show different patterns of enzyme expression. Beard dermal papilla cells express the highest levels of 5-alpha reductase type 1, followed by scalp dermal papilla cells, with ordinary skin fibroblasts expressing much less.²⁶

This uneven enzyme landscape means that even if your bloodstream delivers the same amount of testosterone everywhere, some tissues are manufacturing far more DHT locally than others. Beard skin is a particularly active DHT factory, which is consistent with the strong androgen-dependence of beard growth. Scalp skin in balding areas is similarly active, but the downstream effect there is destruction rather than growth. The follicle’s interpretation of the DHT signal, not just the amount of DHT, determines the outcome.

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