Most men lose their hair because of a hormone called DHT that gradually shrinks hair follicles until they stop producing visible hair. By age 30, roughly 25 to 30 percent of men show signs of hair loss. By 50, half of all men are affected, and by 70, that number climbs to nearly 80 percent. While genetics and hormones drive the vast majority of cases, stress, nutritional gaps, and autoimmune conditions can also play a role.
How DHT Shrinks Your Hair Follicles
The main culprit behind male hair loss is a hormone called dihydrotestosterone, or DHT. Your body naturally converts testosterone into DHT through an enzyme in the scalp. DHT then binds to receptors found exclusively in the dermal papilla cells of hair follicles, the tiny structures at the base of each hair that control growth. Once DHT latches on, it triggers a process called miniaturization: the follicle gradually produces thinner, shorter, lighter hairs with each growth cycle until it eventually stops producing visible hair altogether.
Men who develop pattern baldness tend to have higher activity levels of the enzyme that creates DHT, along with more DHT bound to follicle receptors, compared to men who keep a full head of hair. This is why hair loss follows a predictable pattern. The follicles along your hairline and crown are especially sensitive to DHT, while the hair on the sides and back of your head is largely resistant to it. That ring of remaining hair you see on many older men isn’t random; it reflects which follicles have DHT receptors dense enough to be affected.
Genetics From Both Sides of the Family
You may have heard that baldness comes from your mother’s side. That’s a persistent myth, but the reality is more complicated. Hair loss depends on genes contributed by both parents. Several genes influence how sensitive your follicles are to DHT, how much DHT your body produces, and how quickly miniaturization progresses. If your father, maternal grandfather, or uncles on either side lost their hair, your risk goes up, but there’s no single “baldness gene” and no way to predict exactly when or how much hair you’ll lose based on family history alone.
Stress-Related Hair Loss
Significant physical or psychological stress can trigger a different type of hair loss called telogen effluvium. Unlike pattern baldness, which progresses slowly over years, this kind of hair loss happens relatively fast and affects the entire scalp rather than specific areas. High fevers, major surgery, severe infections, crash diets low in protein, thyroid problems, and intense emotional stress can all push large numbers of hair follicles into their resting phase at once.
The tricky part is the delay. Hair typically starts falling out two to three months after the stressful event, which makes it hard to connect cause and effect. You might not link a bout of illness in January to noticeable thinning in April. The good news is that acute telogen effluvium usually resolves on its own within six months once the underlying trigger is addressed. The follicles aren’t damaged; they’ve just temporarily shut down.
Nutritional Deficiencies That Thin Hair
Low levels of certain nutrients can contribute to hair loss or make existing thinning worse. Iron deficiency and low vitamin D are the two with the strongest evidence linking them to hair shedding. If blood tests confirm a deficiency, supplementing can help. Vitamin C also plays a supporting role because your body needs it to absorb iron from food.
The picture gets murkier with other supplements. The evidence for zinc, biotin, selenium, and B vitamins is conflicting, and loading up on them without a confirmed deficiency won’t necessarily help. In fact, excessive intake of vitamin A and selenium can actually increase hair loss. This is one area where more is not better, and blood work matters more than guesswork.
Autoimmune Hair Loss Looks Different
Alopecia areata is an autoimmune condition where the immune system attacks hair follicles directly. It looks very different from pattern baldness. Instead of a gradually receding hairline, it causes sudden, round patches of hair loss about the size of a quarter. These patches can appear on the scalp, beard, eyebrows, or anywhere on the body. Some people also notice small dents or pits in their fingernails that make the surface feel gritty, like sandpaper.
A doctor can usually diagnose alopecia areata just by examining the bald patches. Characteristic signs include tiny black dots in the follicle openings (broken hair shafts), short hairs that taper toward the scalp like exclamation points, and occasionally white hairs growing back in affected areas. Unlike pattern baldness, alopecia areata can reverse on its own, though it often recurs unpredictably.
What Treatment Actually Achieves
For pattern baldness, two main approaches have solid clinical backing. One is a topical or oral medication that stimulates blood flow to follicles and encourages growth. The other blocks the enzyme that converts testosterone to DHT, reducing the hormone levels at the follicle. These are often used together.
A large retrospective study of 502 men using a combination approach found that 92.4 percent were either stable or improved after 12 months, with 57.4 percent showing clear regrowth. Even men with advanced hair loss (significant balding across the crown and top) saw results, with half to two-thirds in that group regrowing hair. These numbers are encouraging, but they come with an important caveat: treatment works best when started early, before follicles have fully miniaturized. Once a follicle has been dormant for years, it becomes much harder to revive.
Stopping treatment typically means the hair loss resumes, because the underlying hormonal process hasn’t changed. For men who want a permanent solution, hair transplant surgery relocates DHT-resistant follicles from the back and sides of the scalp to thinning areas. These transplanted follicles retain their resistance to DHT in their new location, which is why transplanted hair tends to last.
Pattern Baldness vs. Other Causes
The pattern of your hair loss tells you a lot about the cause. Gradual thinning that starts at the temples or crown and progresses over years almost always points to DHT-driven pattern baldness. Sudden, diffuse shedding across the whole scalp, especially a few months after a major life event, suggests telogen effluvium. Distinct round patches, particularly with nail changes, point toward alopecia areata.
These distinctions matter because the treatments are completely different. DHT-blocking medications won’t help autoimmune hair loss, and waiting out telogen effluvium won’t slow pattern baldness. If your hair loss doesn’t fit the typical pattern, or if it came on suddenly, identifying the actual cause is the first step toward the right approach.