Male Pattern Baldness Explained: What DHT Actually Does

Welcome to the Trailhead. You have probably already done the thing where you tilt your head under the bathroom light, photograph your crown from an angle no human has ever seen you from, and zoom in like a forensic analyst. The internet then informed you it was your shampoo, your hat, your mother, or a mysterious “scalp tension” that only a $90 gadget can release.

Let me save you a few late nights. Male pattern baldness is a hormone and genetics story, and the hormone has a name: dihydrotestosterone, or DHT. Once you understand what DHT is doing up there, the pattern, the timing and the treatments all make sense. Here is The Map.

Key facts

• Male pattern baldness (androgenetic alopecia) affects an estimated 50 million men in the United States ¹.
• The hormone driving it is DHT, which acts on hair follicles that are genetically more sensitive to it ¹.
• Affected follicles shrink over time and produce shorter, finer hairs until they stop growing ²³.
• Loss shows up at the temples and crown, while the back and sides usually keep their hair ²³.
• About half of white men show visible signs by age 50 and about 80 percent by age 70 ²⁴.
• Without treatment it keeps progressing; finasteride and minoxidil are the two FDA-approved medicines that slow it ²⁴⁶.

What does DHT actually do to hair follicles?

DHT is an androgen made from testosterone by an enzyme called 5-alpha reductase, and in men with male pattern baldness it shortens the growth phase of susceptible follicles ¹². The type 2 form of that enzyme lives predominantly in the outer root sheath of the follicle itself, so the conversion happens right where the damage shows up ².

Every hair cycles through a long growth phase (anagen), a short transition, and a rest before it sheds. When DHT stimulates the androgen receptor in a susceptible follicle, anagen gets a little shorter with each cycle and the follicle miniaturizes: the hair it makes gets thinner and shorter, until eventually it may not reach the surface at all ². The balding scalp in affected men contains miniaturized follicles and more DHT than the still-hairy scalp on the same head ⁵.

Worth saying plainly: men with completely normal hormone levels bald every day. The difference is how sensitive the follicle is, and that is where your genes come in.

Why do the temples and crown go first, and why do the sides stay?

Follicles in different parts of the scalp respond differently to the same DHT. The temples and crown carry follicles that are highly responsive, so they miniaturize first; the follicles across the back and sides are far less responsive, which is why they keep producing normal hair even in advanced baldness ²³⁵.

That regional difference creates the classic sequence: the hairline recedes into an “M,” the crown thins into a bald spot, and the two areas eventually meet, leaving a horseshoe of hair around the sides and back ³. Dermatologists grade the progression with the Norwood-Hamilton scale ². It is also why hair transplants work at all: hair moved from the back keeps behaving like back hair.

Is male pattern baldness genetic?

Yes, strongly, though not in the tidy way the internet claims. The only gene with confirmed involvement is the androgen receptor (AR) gene, and certain variations make receptors “more easily stimulated by androgens than normal” ¹. But the condition is polygenic, influenced by genes from both your mother’s and your father’s side, and the inheritance pattern is officially described as unclear ¹².

So the maternal-grandfather rule is a myth with a grain of truth. The AR gene sits on the X chromosome, which comes from your mother, but plenty of other genes matter too, and sons of fathers who balded have roughly five to six times the relative risk ². Looking at both sides of the family gives you a rough forecast rather than a verdict.

How common is it, and when does it start?

Very common, and earlier than most men expect. More than half of men over 50 have some degree of it ¹. Among white men, roughly half show signs by age 50 and about 80 percent by 70; prevalence is somewhat lower in Asian and African American men ².

Onset can come in the late teens or early twenties, though it more often appears later ⁴. If you are 24 and watching your temples, you are not early or unlucky. You are on schedule, with the most hair to protect.

What actually stops male pattern baldness?

Two FDA-approved medicines have been shown to slow it: topical minoxidil, sold over the counter, and prescription finasteride 1 mg daily ²⁴. Finasteride blocks the conversion of testosterone to DHT, and in the AAD’s summary of the evidence it slowed further loss in about 80 to 90 percent of men, with results usually visible around six months ³⁴. Minoxidil works differently, stimulating the follicle rather than lowering DHT, and can take six to twelve months to show results ⁴. You can read the details on the finasteride page.

Both are maintenance medicines. Once you stop, the DHT is still there and the loss resumes ³⁴. This is Root Work: unglamorous, daily, and the entire reason the trail stays open. Hair transplants and platelet-rich plasma injections are also options for some men ⁴. What does not stop it: most of what is sold next to the shampoo. We have a whole article on the myths.

When to talk to a clinician

Male pattern baldness is slow, symmetrical and painless. If your hair loss is sudden, patchy, itchy, painful or scaly, or hair is coming out in clumps when you wash or comb, that is a different trail and needs a real evaluation. Thyroid disease, alopecia areata, scalp infections and certain medications all cause hair loss that looks nothing like a Norwood pattern, and sudden hair loss can signal an underlying condition that needs treatment ⁶⁷.

If your pattern does look like the classic one, the best time to make a plan is now, because these treatments preserve hair far better than they regrow it, and without treatment the loss continues ⁴⁶. Take a few Trail Marker photos in good light for a baseline.

Bring those bathroom-light photos to a $45 consult. We will look at them the way you did, minus the panic.

Hairy questions, straight answers

Is DHT the only cause of male pattern baldness?

DHT is the hormone that drives it, but it only causes hair loss in follicles that are genetically sensitive to it. Men with normal hormone levels bald all the time; the difference is in the follicle, which is why treatment focuses on lowering DHT at the follicle or stimulating the follicle directly.

Does male pattern baldness come from your mother's side?

Partly. The androgen receptor gene, the only gene confirmed to be involved, sits on the X chromosome you get from your mother. But the condition involves many genes from both parents, and the inheritance pattern is officially unclear. Looking at both sides of the family gives you a rough forecast rather than a verdict.

At what age does male pattern baldness start?

It can start in the late teens or early twenties, though it more often shows up later. About half of white men have a visible sign by age 50 and roughly 80 percent by 70. Starting early is common and is also when treatment has the most hair to protect.

Why does hair on the back and sides never fall out?

Follicles on the back and sides of the scalp are far less responsive to DHT than follicles at the temples and crown, so they keep growing normal hair even in advanced baldness. That is also why transplanted hair taken from the back keeps growing in its new location.

Can male pattern baldness be stopped completely?

It can be slowed substantially for many men. Finasteride slowed further loss in about 80 to 90 percent of men in the AAD's summary of the evidence, and minoxidil helps many men keep or regrow hair. Both work only while you keep using them; hair loss resumes after stopping.

Sources

1. MedlinePlus Genetics: Androgenetic alopecia ↗
2. StatPearls (NCBI Bookshelf): Androgenetic Alopecia ↗
3. MedlinePlus Medical Encyclopedia: Male pattern baldness ↗
4. American Academy of Dermatology: What is male pattern hair loss, and can it be treated? ↗
5. DailyMed: finasteride 1 mg tablets prescribing information ↗
6. American Academy of Dermatology: Hair loss, who gets and causes ↗
7. Mayo Clinic: Hair loss, symptoms and causes ↗

Information checked 2026-09-13 by LPMD Medical Group clinicians. This article is general education, not a diagnosis or a treatment plan for you. Your clinician and pharmacist provide the instructions for your actual prescription.