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About 95% of thinning hair is caused by male pattern hair loss, also known as androgenetic alopecia. Male pattern hair loss is caused by DHT (dihydrotestosterone), a type of sex hormone known as an androgen. Androgens contribute to typical male characteristics, such as a deeper voice, increased muscle mass, and body hair. DHT, in particular, is part of what makes us male: It aids in the development of male genitalia in utero.
But DHT giveth and DHT taketh away. Although DHT is crucial to the formation of pubic hair and body hair, it can cause you to lose the hair on your scalp. Researchers aren’t entirely sure why. But by age 50, more than half of American men will experience hair loss caused by DHT.
- Male pattern baldness is caused by DHT (dihydrotestosterone), a sex hormone known as an androgen.
- In genetically susceptible people, DHT causes hair follicles to shrink and make thinner, shorter hairs.
- The oral medication finasteride (brand name Propecia) is an effective inhibitor of DHT.
- Other therapies can be used in conjunction with finasteride, like minoxidil and DHT-blocking shampoos, to address certain kinds of hair loss.
What does DHT do?
DHT is a derivative of testosterone, a sex hormone you might have heard a bit about. In men, the enzyme 5-alpha-reductase converts testosterone into DHT. After it’s created, DHT flows freely through your bloodstream and can link to androgen receptors on hair follicles in your scalp, if you’re genetically predisposed to it. That causes them to shrink, gradually getting smaller and smaller and producing less robust hair.
It’s a myth that men who are losing their hair have more testosterone than guys with luscious locks. It just means the androgen receptors in their hair follicles are more sensitive to the effects of DHT.
Besides hair loss, research has linked high levels of DHT to prostate issues (including an enlarged prostate).
What is a DHT blocker?
Treatments that block or inhibit the production DHT may help prevent hair loss.
A DHT blocker is an oral or topical medication or product that works to prevent testosterone from converting into DHT and hanging around in follicles, where it can do damage.
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How DHT contributes to baldness
It is estimated that each of us has about 100,000 hairs on their scalp, and we lose about 100 hairs a day. That’s part of the natural hair life cycle — the hair follicles on our scalp are in the continuous process of growing and shedding hair. Hair increases in length by about one-half inch a month or six inches a year, and growth happens in three distinct phases:
Anagen is the growth phase. Scalp hairs remain in this phase for 2 to 6 years. The relative length of the anagen phase is one reason why hair grows to different lengths on your body (i.e., why your eyebrows don’t keep growing). Most hairs (about 80 to 90%) on your scalp are in this phase right now.
Catagen is a very short phase —14 to 21 days)—when a hair stops growing and detaches from its blood supply.
Telogen is the resting phase, in which the hair follicle lies dormant for about three months until the hair falls out. About 10 to 20 percent of the total hair on your scalp is in this phase at a given time. After this, anagen normally begins again.
But high levels of DHT shrink the hair follicles, shortening the growth phase and creating thinner hair called vellus hair. This process is called follicular miniaturization. For a time, follicular miniaturization is a reversible process. This means that certain hair-loss medications like finasteride and minoxidil can actually reverse hair loss, by increasing follicle size again and promoting the growth of more robust hairs, called terminal hairs. However, as more time goes on, changes continue to happen to the follicle, making the reversal of hair loss less likely. One hypothesis is that the detachment of the follicle from the underlying muscle (called the arrector pili muscle) causes an irreversible process (Sinclair, 2015).
DHT and genetics
Genes determine whether you will preserve hair into your 60s or start losing it in your 20s. A recent study found that there are over 250 genetic areas that influence male pattern baldness, and they can be inherited from either parent (Hagenaars, 2017).
Researchers believe that some people are more susceptible to DHT’s damaging effects on hair because of variations in their androgen receptor (AR) gene. Those variations can increase androgen receptivity in your scalp follicles, making you more likely to experience hair loss.
You may have heard that male pattern hair loss comes from your mother’s father, and this can be true in some. The AR gene resides on the X chromosome, so individuals with a maternal grandfather who had male pattern baldness have a 50 percent chance of receiving the X chromosome from him (through the mother) that carries the same AR gene.
How to reduce DHT
If you’re experiencing male pattern hair loss, you can take action to stem the loss and increase hair growth by reducing or blocking DHT.
There is one therapy that has been proven to reduce DHT, other remedies that claim to do so, and other things you can use in conjunction with DHT blockers to slow or reverse male pattern baldness.
Finasteride (brand name Propecia)
Finasteride is an oral medication known as a 5-alpha-reductase inhibitor. 5-alpha-reductase converts testosterone into DHT. When it is inhibited, so is the production of DHT. When used for hair loss, finasteride is taken at a dosage of 1mg a day.
The American Hair Loss Association says finasteride stopped hair-loss progression in 86% of men who took the drug in clinical trials, and 65% of them experienced increased hair growth (AHLA, n.d.).
According to a 2017 meta-analysis of studies published in the Journal of the American Academy of Dermatology, finasteride was found to be superior to placebo in regrowing hair. The researchers concluded it’s effective for promoting hair growth in men with male pattern baldness (Adil, 2017).
Several varieties of shampoo claim to block DHT’s effects on hair follicles. They’re considered less effective than finasteride. Some of these shampoos contain zinc, vitamin B12, or ketoconazole (the active ingredient in the dandruff shampoo Nizoral). It is hypothesized that ketoconazole, in combination with finasteride, can disrupt DHT’s effects on the scalp (Hugo Perez, 2004).
Side effects of blocking DHT
The good news is that the majority of men who use a DHT blocker such as finasteride don’t experience side effects. But some men who’ve taken finasteride have reported sexual side effects, including a reduced sex drive, trouble getting or keeping an erection, or a reduced volume of semen. In most cases, side effects go away after discontinuing the medication. Read more about finasteride and possible side effects here. Side effects are more likely in the higher doses of finasteride that are taken for benign prostate hyperplasia (BPH). Women and children should NOT take finasteride.
Other ways to address male pattern baldness
Minoxidil (brand name Rogaine)
Minoxidil is an over-the-counter liquid or foam that is applied to the scalp twice a day. It’s known as a peripheral vasodilator, which helps widen and loosen blood vessels to increase blood flow. If you stop using it, the new growth may reverse, and hair loss will continue.
Minoxidil doesn’t have a direct effect on DHT. But studies show that using minoxidil and finasteride together is more effective than using either one alone (Chandrashekar, 2015). (Minoxidil will be effective whether it’s the pricey brand preparation, Rogaine, or the inexpensive version sold online for a few dollars a bottle.)
A red light therapy device
Low-level laser light therapy (LLLT) is an FDA-cleared way to treat hair loss. These devices might come in the form of a wand you point at the scalp or a cap you can wear. They emit a constant red LED light that is believed to reduce inflammation and increase blood flow to the hair follicles.
According to the 2017 meta-review published in the Journal of the American Academy of Dermatology, both minoxidil and LLLT were found to be effective in regrowing hair lost to male pattern baldness (Adil, 2017).
PRP (platelet-rich plasma) treatments
Several dermatologists and hair-replacement specialists offer this treatment, in which a patient’s blood is drawn and placed in a centrifuge to extract the plasma, which is then injected into the scalp. The theory is that the growth factors in platelets can spur hair growth. A 2017 study published in the International Journal of Molecular Sciences found that PRP treatment increased the number of hairs and overall hair density versus areas treated with a placebo (Gentile, 2017).
Hair transplantation is a surgical procedure that moves hair from one place on the scalp to another. The hairs on the back and side of the head are more resistant to DHT, even into old age, than hairs on the top of the head. So when hair is moved from the sides of the scalp into areas of male pattern baldness, it can provide a long-lasting solution.