Male pattern baldness is caused by a combination of genetics and hormones, specifically the way your hair follicles respond to a hormone called dihydrotestosterone (DHT). It’s not about having too much testosterone. It’s about how sensitive your follicles are to DHT, and that sensitivity is largely written into your DNA. Roughly 30% of men show signs by age 30, 50% by age 50, and the numbers keep climbing with each decade.
DHT and Follicle Miniaturization
Your body naturally converts testosterone into DHT using an enzyme called 5-alpha reductase. DHT is more potent than testosterone and plays important roles during puberty, but in the scalp, it can cause real damage to hair follicles over time. When DHT binds to receptors on a hair follicle, it triggers a process called miniaturization: the follicle gradually shrinks, producing thinner, shorter, lighter hairs with each growth cycle until it eventually stops producing visible hair altogether.
This doesn’t happen evenly across the scalp. The frontal hairline and crown have significantly higher concentrations of 5-alpha reductase and androgen receptors compared to the back and sides of the head. That’s why balding follows a predictable pattern, receding at the temples and thinning on top, while the hair around the sides and back stays thick. It’s also why hair transplants work: follicles taken from the back of the scalp are naturally resistant to DHT and keep that resistance even after being moved.
How Your Hair Growth Cycle Changes
Each hair on your head cycles through three phases: a growth phase lasting 2 to 6 years, a brief transition phase, and a resting phase of several months before the hair falls out and a new one begins growing. DHT disrupts this cycle in two ways. First, it shortens the growth phase, so each new hair has less time to reach full length and thickness. Second, the replacement hair that grows in after a strand falls out is delayed, meaning follicles spend more time sitting empty.
Over repeated cycles, the effect compounds. A follicle that once produced a thick terminal hair starts producing a fine, pale vellus hair (the kind of peach fuzz you see on a child’s arm). Eventually the follicle becomes so small it can’t produce any visible strand at all. This is why early intervention matters: once a follicle has fully miniaturized, it’s much harder to revive.
Genetics Play the Biggest Role
Male pattern baldness is polygenic, meaning multiple genes contribute. The most well-studied is the androgen receptor gene, which sits on the X chromosome. Since men inherit their X chromosome from their mother, this is where the old advice about “look at your mother’s father” comes from. Research has found that a specific genetic marker on the androgen receptor gene is present in about 98% of young bald men, compared to roughly 77% of men without hair loss. Shorter repeat sequences within this gene are also more common in men who go bald, and a balding scalp shows increased expression of the androgen receptor gene itself.
But the X chromosome isn’t the whole story. Studies have identified risk variants on other chromosomes inherited from both parents, which is why some men go bald even when their maternal grandfather had a full head of hair. If your father is bald, that still raises your risk. The condition requires several genetic factors to align, and the more of them you carry, the earlier and more extensively hair loss tends to progress.
It’s Not About High Testosterone
One of the most persistent misconceptions about male pattern baldness is that it signals high testosterone levels. In reality, men who go bald don’t necessarily have more testosterone or more DHT circulating in their blood than men who keep their hair. The difference is local: their scalp follicles are genetically programmed to be more sensitive to DHT. Two men with identical hormone levels can have completely different hairlines simply because their follicles respond differently.
That said, the enzyme 5-alpha reductase is more active in the scalps of men compared to women. Men’s frontal follicles contain roughly 3 to 3.5 times more of this enzyme than women’s frontal follicles, which partly explains why the condition is so much more common and severe in men.
Inflammation May Accelerate the Process
Male pattern baldness has traditionally been classified as noninflammatory hair loss, but that picture is changing. Scalp biopsies from men with the condition show immune cell clusters around hair follicles in nearly 88% of cases. This inflammation tends to concentrate in the upper portions of the follicle, and it’s closely tied to miniaturization: in one study, inflammation was found adjacent to miniaturized follicles in 86% of cases, with some severely shrunken follicles surrounded by intense inflammatory activity.
Researchers aren’t yet certain whether inflammation drives miniaturization or results from it, but the association is strong enough that it likely plays a role in progression. This may be one reason why some men respond to treatments that reduce scalp inflammation alongside standard therapies.
Insulin Resistance and Metabolic Health
There’s growing evidence that metabolic factors can influence how quickly and severely hair loss progresses. A study of men under 30 with significant balding found that 44% had insulin resistance, a condition where the body struggles to regulate blood sugar effectively. Men who had both insulin resistance and hormonal imbalances were significantly more likely to have advanced hair loss compared to those with only one factor or neither.
This doesn’t mean insulin resistance causes male pattern baldness on its own. Genetics still set the stage. But metabolic health appears to amplify the hormonal signals that drive follicle miniaturization, particularly in younger men who develop noticeable thinning earlier than expected. Maintaining a healthy weight and staying physically active may not prevent baldness, but it could influence the pace of progression.
How Hair Loss Typically Progresses
Male pattern baldness follows a fairly predictable path, mapped out on a seven-stage scale developed by dermatologists. In the earliest stage, the hairline shifts slightly, forming what’s called a mature hairline. This is common in most adult men and isn’t necessarily a sign of progressive loss. By stage 3, the recession at the temples becomes pronounced, forming an M or V shape, and this is generally considered the first stage of clinically significant balding. Some men also develop a thinning spot at the crown around this time.
From there, the receding hairline and the crown spot gradually expand and merge. In the most advanced stage, only a horseshoe-shaped band of hair remains around the sides and back of the head. Not every man progresses through all stages. Some stabilize at an early stage and stay there for decades, while others move through the stages relatively quickly, especially if hair loss starts in their late teens or early twenties.
Current Treatment Options
Only two treatments are FDA-approved for male pattern baldness: minoxidil (a topical liquid or foam applied directly to the scalp) and finasteride (an oral tablet). They work through completely different mechanisms. Minoxidil stimulates blood flow to follicles and can extend the growth phase of the hair cycle. It’s been available since 1987 and doesn’t require a prescription. Finasteride blocks the enzyme that converts testosterone to DHT, reducing DHT levels in the scalp and slowing miniaturization.
Both treatments work best when started early, before significant follicle miniaturization has occurred. They can slow further loss and, in many cases, partially reverse thinning by allowing shrunken follicles to recover. The main limitation is that both require ongoing use. Stopping treatment typically means hair loss resumes within several months as DHT activity picks back up. Hair transplant surgery offers a more permanent option by relocating DHT-resistant follicles from the back of the scalp to thinning areas, though it works best in combination with medical therapy to protect the remaining native hair.