Dihydrotestosterone (DHT) Can Cause Baldness, But What Is It?

When you start losing your hair, you have questions. First and foremost: What's making this happen? While modern medicine has given us many ways to fight balding, our understanding of what causes male pattern baldness is still a little, well, patchy. That's not good news for any of us, considering that by age 35, around two thirds of American men will be dealing with some degree of hair loss, according to the American Hair Loss Association. By age 50, it's up to 85%. Here's what we do know: your chances of keeping your hair hinge on how sensitive you are to something called Dihydrotestosterone (DHT). If you've Googled male pattern baldness, you've probably seen those three letters. But unless you're a doctor, you were probably as confused as we were at first. So let's break it down: Here's what we know about DHT, and what it's doing in your body—and to your scalp.

One of the popular myths about balding is that it’s a sign you have more testosterone than other guys. Strictly speaking, that’s not correct. You can have as much testosterone as ‘80s Arnold Schwarzenegger, but what really matters is how much of it converts to DHT. “DHT is a modified, more active form of testosterone,” explains Joshua Zeichner Director of Cosmetic and Clinical Research in Dermatology at Mount Sinai Hospital in NYC. “In your body, testosterone is transformed into DHT, which exerts stronger effects than testosterone itself.” In fact, DHT is estimated to be five times more potent than the regular stuff. So even if you’re a low-testosterone kind of guy, if your body is converting it heavily, you’re in trouble.

Let’s get one thing clear: DHT isn’t all bad. In fact, without it we wouldn’t be men in the first place. DHT helps develop our genitals in utero—meaning it makes us boys in the first place. It’s a “sex steroid,” so it also does the heavy work during puberty, lowering our voices and putting hair on our chests. How do we know DHT is linked to balding? First, hairs plucked from the scalps of balding men test higher for levels of DHT. Second, when we decrease levels of DHT in the body, we see hair loss slow or even reverse—more on that in a minute. Here’s what we think DHT is doing. As hair on the scalp goes through its normal cycle of growing and shedding, DHT makes the follicles miniaturize. That means they get thinner—and shorter, because the growing cycle doesn’t last as long. In some cases, the growing cycle becomes so brief that new hairs don’t even poke through the skin. Plus, the thinning of the hairs makes them easier to shed. The result is classic “male pattern” baldness, the kind of balding that produces what the American Hair Loss Association calls a “horseshoe” shape, with hair growing from the temples and around the back of the head. So if we know DHT is to blame for male pattern baldness, why haven’t we fixed this problem? Well, in some of our bodies, head hair and DHT co-exist in peace.

But others of us are born with a genetic sensitivity to this particular sex steroid. A 2017 study from the University of Edinburgh identified 287 genetic regions that contribute to male pattern baldness. It was the largest genetic analysis of bald men to date, and could provide targets for drug development. But there's still much more work to be done to link which genes are interacting with DHT in what ways. Until we’re able to pinpoint or modify the “baldness gene,” what’s a man to do? “Medications such as finasteride target the enzyme that converts testosterone into DHT,” says Zeichner. “By lowering the levels of DHT, the drug helps maintain or enhance regrowth of hair on the scalp.” You know finasteride as Propecia. It’s also sold under the brand name Proscar. Rather than working on the hair follicles themselves, it inhibits the 5-AR enzyme, the one responsible for DHT conversion. A single milligram dose of finasteride can lower DHT levels by 60%, and the American Hair Loss Association says it stops the progression of hair loss in 86% of men taking it in clinical trials. 65% of them experienced increased hair growth. 85% of us will suffer by age 50, but 86% of us can stop balding—at least for as long as we take the drug. Until we can reprogram our genes, those might be odds you want to take.