Male baldness is primarily caused by a combination of genetics and hormones that gradually shrink hair follicles until they stop producing visible hair. This process, called androgenetic alopecia, affects roughly two-thirds of men by age 35 and about 85% by age 50. Around 25% of men who will experience pattern baldness start noticing hair loss before they turn 21.
How Hormones Shrink Hair Follicles
The central driver of male pattern baldness is a hormone called DHT (dihydrotestosterone). Your body converts testosterone into DHT using an enzyme found in both the skin and the prostate. DHT binds to receptors on hair follicles in specific areas of the scalp, particularly the temples and crown. Once it attaches, it triggers a process called miniaturization: the follicle gradually produces thinner, shorter, lighter hairs with each growth cycle until it eventually stops producing hair altogether.
Not every follicle on your head is equally sensitive to DHT. The follicles along the sides and back of the scalp are largely resistant, which is why even men with severe baldness typically keep hair in a horseshoe pattern around the lower scalp. The follicles on top are genetically programmed to respond to DHT, and how strongly they respond determines how much hair you lose and how fast.
Genetics Are Far More Complex Than “Your Mom’s Side”
The old advice to look at your mother’s father to predict your hair loss is oversimplified. While the androgen receptor gene on the X chromosome (which you inherit from your mother) plays a significant role, it’s only one piece of a much larger genetic puzzle. A large-scale genetic study published in PLOS Genetics identified over 250 independent genetic locations associated with severe hair loss, with 247 of those on non-sex chromosomes, meaning they can come from either parent.
Many of these genes are linked to processes you wouldn’t immediately connect to baldness. Some are involved in hair follicle development, others in hair growth regulation, and some are associated with seemingly unrelated traits like gray hair or eyebrow thickness. Genes that control how hair follicle stem cells communicate also appear on the list. One gene, for instance, is linked to hair growth patterns in dogs, while another is associated with coat growth in mice. The takeaway: baldness runs in families, but it’s influenced by hundreds of genetic variants from both sides of your family tree, not a single inherited switch.
The Role of Inflammation
Male pattern baldness has traditionally been classified as non-inflammatory, but newer research tells a more nuanced story. Histological and molecular evidence shows that chronic, low-grade micro-inflammation develops around the upper portions of hair follicles in balding scalps. This subtle inflammation is a feature of the early stages of baldness and precedes scarring (fibrosis) around the follicles in later stages, suggesting it plays a meaningful role in accelerating hair loss rather than being a mere bystander.
This doesn’t mean baldness is an inflammatory disease in the way that, say, psoriasis is. But it does mean that the health of your scalp environment matters. Persistent irritation, whether from untreated dandruff, seborrheic dermatitis, or other scalp conditions, may compound the follicle damage that DHT is already causing.
Temporary Hair Loss vs. Permanent Baldness
Not all male hair loss is pattern baldness. A condition called telogen effluvium causes sudden, diffuse thinning across the entire scalp rather than the receding hairline or crown thinning typical of androgenetic alopecia. It’s triggered by physical or emotional stress: high fevers, surgery, severe infections, crash diets, iron deficiency, thyroid problems, or major life upheavals. The stress pushes a large percentage of hair follicles into their resting phase all at once. After one to six months, those hairs fall out in clumps, which can be alarming.
The key differences are important to recognize. Telogen effluvium happens suddenly, affects the whole scalp evenly, leaves your hairline intact, and is temporary. Pattern baldness develops gradually over years or decades, follows a predictable pattern starting at the temples and crown, and is permanent without treatment. Men can experience both simultaneously, which sometimes makes the situation confusing. If your hair loss came on fast and doesn’t follow the typical receding pattern, stress-related shedding is worth investigating.
How Pattern Baldness Progresses
Male pattern baldness follows a well-documented progression. It typically begins with a slight recession at the temples, creating what’s sometimes called a “mature hairline.” This alone isn’t necessarily a sign of significant balding. The first clinically significant stage involves the hairline receding deeply at both temples into an M, U, or V shape, with those recessed areas becoming completely bare or very sparsely covered. From there, thinning usually spreads to the crown, and eventually the two areas merge, leaving hair only on the sides and back.
The speed of this progression varies enormously. Some men go from a full head of hair to significant baldness in under a decade. Others experience slow thinning that takes 25 years or more to become noticeable. Your genetics largely determine the pace, though other factors can accelerate it.
Nutritional and Lifestyle Factors
Nutrient deficiencies won’t cause pattern baldness on their own, but they can worsen thinning or trigger additional shedding on top of genetic hair loss. Low vitamin D levels and confirmed iron deficiency are the two nutritional factors with the most evidence behind them. If you’re losing hair and have either deficiency, correcting it through supplementation can improve hair density. The evidence for zinc’s role in hair loss is more mixed.
Smoking, poor sleep, and chronic stress don’t directly cause androgenetic alopecia, but they can push more follicles into the resting phase and contribute to the scalp inflammation that accelerates the balding process. Think of these as factors that can make genetic baldness worse or arrive sooner rather than being root causes on their own.
What Treatment Can Realistically Achieve
The two most established treatments work by addressing the hormonal mechanism behind baldness. One blocks the enzyme that converts testosterone to DHT, reducing DHT levels throughout the body. In clinical studies, 86% of men using this approach either maintained their existing hair or saw increased hair counts after 12 months, compared to only 42% of men taking a placebo. The other treatment is applied directly to the scalp and works by increasing blood flow to follicles and extending the growth phase of the hair cycle.
Both treatments are more effective at maintaining what you have than regrowing what’s already gone. They work best when started early, while follicles are miniaturized but not yet dead. Once a follicle has fully scarred over, no medication can revive it. Hair transplant surgery relocates DHT-resistant follicles from the back and sides of the scalp to balding areas, and because those follicles retain their resistance to DHT, the transplanted hair is permanent.
Research at UC Irvine has identified a signaling molecule called SCUBE3 that dermal papilla cells naturally produce to tell neighboring hair stem cells to start dividing and begin new growth. This discovery could eventually lead to treatments that directly activate dormant follicles, though it hasn’t yet reached the clinic.