Men go bald primarily because a hormone called DHT shrinks their hair follicles until those follicles can no longer produce visible hair. By age 35, roughly two-thirds of men will notice some degree of hair loss, and by 50, about 85% will have significantly thinner hair. The process is driven by genetics, hormones, and time, not by wearing hats, using too much shampoo, or any of the other popular theories that float around.
How DHT Shrinks Hair Follicles
Testosterone circulating in your bloodstream gets converted into a more potent hormone called dihydrotestosterone, or DHT. On its own, DHT plays useful roles in the body. The problem starts when DHT binds to receptors on hair follicles that happen to be sensitive to it, typically the ones along your hairline, temples, and crown.
When DHT latches onto these follicles, it gradually causes them to miniaturize. Thick, pigmented “terminal” hairs are replaced by thinner, shorter, nearly transparent hairs. Over time, those wispy hairs stop growing altogether, and the scalp appears smooth and bald. Simultaneously, the active growth phase of each hair shortens dramatically. A healthy hair follicle grows for four to six years before resting and shedding. In men experiencing pattern baldness, that growth window can collapse to a year or less, meaning hairs fall out before they ever reach noticeable length.
This is why baldness looks gradual rather than sudden. It’s not that hair falls out all at once. Each follicle slowly produces a weaker version of the hair it used to grow, cycle after cycle, until it produces nothing at all.
Why Some Men Lose Hair and Others Don’t
The difference comes down to genetics, specifically how sensitive your hair follicles are to DHT. All men produce DHT, but not all men’s follicles respond to it the same way. The key gene identified so far is the AR gene, which provides instructions for building androgen receptors. Variations in this gene can make those receptors more easily activated by DHT, essentially turning up the volume on the hormone’s signal to shrink follicles.
The AR gene sits on the X chromosome, which men inherit from their mothers. This is why people often say baldness comes from your mother’s side, and there’s some truth to it. But the full picture is more complicated. Pattern baldness clusters in families on both sides, and researchers suspect multiple genes beyond AR contribute to the condition. Having a close relative with significant hair loss, whether that’s your father, grandfather, or uncle, increases your risk regardless of which side of the family they’re on.
The Typical Pattern of Loss
Male pattern baldness follows a recognizable progression, which doctors classify using a seven-stage scale called the Norwood scale. It almost always starts the same way: a slight recession at the temples, creating a more pronounced “M” shape to the hairline. Many men notice this in their 20s or early 30s and assume it’s just a maturing hairline, which is sometimes accurate. A mild recession at the temples (stage 2) is common and doesn’t necessarily mean further loss is coming.
When baldness does progress, it typically moves backward from the temples while simultaneously thinning at the crown. Eventually those two thinning zones connect, leaving a horseshoe-shaped ring of hair around the sides and back of the head. The hair on the sides and back survives because those follicles are genetically resistant to DHT, which is also why they’re used as donor hair in transplant procedures. Hair loss can begin any time after puberty and progress over years or decades. Some men reach advanced stages by their 30s, while others thin slowly over a lifetime.
Temporary Shedding vs. Permanent Baldness
Not all hair loss in men is permanent pattern baldness. A condition called telogen effluvium causes large numbers of follicles to enter their resting phase simultaneously, leading to diffuse shedding across the entire scalp. You might lose 300 to 500 hairs per day instead of the normal 50 to 100. It typically starts about three months after a triggering event: surgery, severe illness, major stress, rapid weight loss, or a medication change.
The key differences are pattern and timeline. Telogen effluvium thins hair evenly across the scalp rather than concentrating at the temples and crown. It comes on relatively suddenly rather than creeping in over years. And it resolves on its own once the trigger is removed. Pattern baldness, by contrast, is progressive and permanent without treatment. If your hair loss follows the classic receding-temples-and-thinning-crown pattern and has been gradually worsening, it’s almost certainly androgenetic alopecia.
Nutrition’s Role (and Its Limits)
Low levels of certain nutrients can cause hair thinning that makes pattern baldness look worse than it is, or that mimics it entirely. Vitamin D is essential for building the cells that develop into hair follicles. Iron carries oxygen to follicles so they can grow. Deficiencies in either can contribute to noticeable thinning.
That said, nutrient shortfalls are rarely the sole cause of hair loss in men. If your thinning follows the classic male pattern, supplements alone won’t stop it. And overcorrecting with supplements can backfire. Excessive vitamin A and selenium actually increase hair loss, and too much biotin (a popular ingredient in hair supplements) can interfere with lab tests, potentially masking other health issues. Fixing a genuine deficiency can help your remaining hair look fuller and healthier, but it won’t override the hormonal process driving pattern baldness.
What Actually Works for Treatment
Two treatments have the strongest evidence behind them. Minoxidil is a topical solution you apply directly to the scalp. In a large study tracking men using the 5% formulation over one year, 62% saw their area of hair loss get smaller, 35% stayed the same, and only about 3% got worse. Roughly 16% of users saw results the investigators rated as “very effective,” while another 48% were rated “effective.” The treatment also cut the number of hairs lost during washing roughly in half, from about 70 per wash down to 34.
The other main option is an oral medication that works by blocking the enzyme that converts testosterone into DHT, reducing DHT levels in the scalp. It’s generally more effective than minoxidil for maintaining existing hair and can produce modest regrowth, particularly at the crown. Both treatments work best when started early in the process. Neither is a cure. Stopping either one allows hair loss to resume where it left off.
Hair transplant surgery remains the most dramatic option. It relocates DHT-resistant follicles from the back and sides of the scalp to thinning areas. Because those follicles are genetically programmed to keep growing, the results are permanent, though the procedure doesn’t prevent continued thinning in untreated areas.
Environmental Factors That Speed Things Up
While genetics and hormones run the show, environmental stressors can accelerate the process. UV radiation triggers the production of free radicals in scalp skin, which can damage follicle cells and promote inflammation. This oxidative stress doesn’t cause pattern baldness on its own, but it creates a harsher environment for follicles that are already under hormonal pressure. Chronic scalp inflammation, whether from UV exposure, pollution, or other irritants, can push vulnerable follicles toward miniaturization faster than they’d otherwise get there.
Smoking, poor sleep, and chronic psychological stress have also been linked to faster progression, likely through similar inflammatory pathways. None of these factors will make a man with DHT-resistant follicles go bald, but for men who are genetically predisposed, they can shave years off the timeline.