If you’ve noticed your hair starting to thin or recede, it’s easy to stress over what’s causing it to happen. Is it stress? A bad diet? Unlucky genetics? Or is it a lifestyle factor you can fix with the right habits?
The reality is that hair loss in men is primarily caused by a combination of genetic factors and a male steroid hormone called dihydrotestosterone (DHT).
DHT can seem complicated, but its role in hair loss is fairly easy to understand once you have a basic knowledge of how your body produces DHT, as well as the damaging effects that DHT can have on your hair follicles.
Below, we’ve explained what DHT is, how it’s produced by your body and the effects it can have on healthy hair growth.
We’ve also covered your options for reducing DHT levels, stopping hair loss and — if you have visible hair loss already — stimulating new hair growth.
DHT, or dihydrotestosterone, is a type of androgen hormone that’s produced by your body as a byproduct of testosterone.
Androgens are hormones that produce male characteristics. They’re responsible for maintaining several aspects of your sexual health and function, as well as secondary sex characteristics and sexual differentiation, such as your bone structure and voice.
Before you’re born, DHT helps to develop your penis and scrotum. As you enter adolescence, it promotes growth of your facial hair, body hair and pubic hair.
It’s one of several hormones that promotes proper sexual development and makes men, well, men.
DHT is created from testosterone, your primary sex hormone that’s produced in your testes. An enzyme called 5-alpha reductase, or 5AR, converts a small percentage of your testosterone into DHT in body tissue like your skin, liver and prostate gland.
Testosterone is also converted to DHT by the 5-alpha reductase enzyme in your scalp, including in your hair follicles.
Most men have much higher levels of testosterone than DHT. According to research, the normal level of DHT in your bloodstream is only around 10 percent of your level of testosterone.
However, because of its potency, DHT can have noticeable effects within your body, even if the total amount of this hormone that circulates in your bloodstream is relatively small.
For example, as an adult, DHT can attach to receptors inside your prostate gland and cause it to grow larger.
This is referred to as benign prostatic hyperplasia (BPH), or enlarged prostate. It’s a common issue for middle-aged and older men.
More famously (and probably why you’re reading this guide), DHT can bind to receptors in your scalp and stop your hair follicles from producing new hairs, resulting in a receding hairline, bald patch at your crown or other signs of male pattern hair loss.
DHT causes hair loss by miniaturizing, or shrinking, the hair follicles around your hairline and on the top of your scalp.
Hair miniaturization sounds complicated, but it’s actually pretty simple. Every hair on your scalp, face and body grows as part of a multi-phase cycle that’s typically referred to as the hair growth cycle.
In the first phase of this cycle, called the anagen phase, each hair grows to its full length. After reaching the end of the growth phase, each hair goes through the catagen and telogen phases, during which it stops growing and is eventually replaced by a new strand of hair.
This continuous process lets you maintain a full head of hair even as your old hairs are shed on a regular basis.
When DHT miniaturizes your hair follicles, it shortens the anagen phase and prevents your hair from growing properly.
Over time, hairs affected by DHT become thinner and shorter, eventually resulting in hair that’s unable to grow through the outer layers of your skin.
This process usually begins at your hairline and crown, resulting in the classic receding hairline or bald patch that many men notice as their first sign of hair loss.
Just like your genes play a major role in determining your height, hair color, eye color and other physical characteristics, they also have a big influence on how susceptible you are to male pattern baldness.
After all, male pattern baldness is referred to as androgenetic alopecia — a word that’s made by fusing together “androgenic” and “genetic.”
Experts think some men have hair follicles that are more sensitive to DHT than others, meaning they miniaturize and stop growing new hairs faster when DHT attaches to receptors in the scalp.
Research also suggests that men affected by male pattern baldness have higher average levels of DHT than their peers, as well as greater concentrations of androgen receptors in the scalp.
This means that if you’re very susceptible to hair loss, you may not just be more sensitive to the effects of DHT than your peers — your body may also be more prone to converting testosterone into DHT, particularly in your hair follicles.
This type of hair loss doesn’t only affect men. Women also make small amounts of testosterone and, therefore, DHT. In women, this is called female pattern hair loss, or FPHL — clever title, we know.
DHT and testosterone are both androgen hormones. However, their functions within your body are different.
As a man, testosterone is a critical hormone for your well-being throughout your life. Maintaining a healthy level of testosterone helps you maintain a normal sex drive, muscle mass and bone health.
Testosterone is also important for maintaining optimal mental function, red blood cell production and energy levels.
As a man, you need testosterone throughout your entire life, from childhood and adolescence to adulthood.
Dihydrotestosterone, on the other hand, is important during childhood and puberty, but it doesn’t play such a major role in your ongoing development as an adult.
As an adult, DHT doesn’t appear to be involved in your mental function, bone health or ability to produce muscle.
Instead, the major effects of DHT in adulthood include contributing to prostate enlargement and causing pattern hair loss.
If you’re genetically predisposed to DHT sensitivity, any kind of increase in your DHT levels may increase your risk of dealing with pattern hair loss. It’s a bummer, but it’s a part of life.
So, what could cause your DHT levels to increase? Well, since DHT is produced as a byproduct of testosterone, it stands to reason that anything that contributes to higher testosterone levels is also likely to contribute to more DHT.
As we’ve covered in our guide to increasing your testosterone levels, a variety of factors all play a role in your testosterone production. These include your diet, sleep habits, the amount of exercise you get and even things like your alcohol consumption.
Most habits that increase testosterone production are good for your health in general, and there isn’t any research showing that these habits cause any noticeable increase in hair shedding.
However, one thing you’ll want to be aware of is that any medications that increase the amount of testosterone in your body could cause increased shedding.
This is something you’ll want to talk about with your healthcare provider, particularly if you have low testosterone and use medication to treat it.
Because DHT is the main hormone responsible for hair loss in men, the most effective way to slow down and prevent hair loss is to block DHT.
Currently, the most effective way to reduce DHT levels is with medication like finasteride. You can also block DHT at the scalp level using medicated shampoos that contain ingredients like saw palmetto.
Finasteride, which is available under the brand name Propecia®, is a prescription medication approved by the FDA that’s used to treat male pattern baldness.
Finasteride reduces DHT levels by inhibiting the effects of 5-alpha reductase — the enzyme that converts testosterone to DHT. By stopping this conversion, finasteride drastically lowers the total amount of DHT your body produces.
You can think of finasteride as a shield that blocks DHT from miniaturizing your hair follicles and contributing to hormonal hair loss.
Research from clinical trials suggests that a normal dose of finasteride can lower DHT levels by 70 percent, which is enough to slow down, stop or reverse hair loss in most men.
This reduction in DHT levels means that your hair follicles are no longer under constant damage due to the effects of DHT.
Finasteride is easy to use. Most men start to notice improvements after around three months of daily use, with the most significant results visible after about one year.
If you’ve ever spent time browsing the men’s shampoo section of your local drug store, you’ve likely seen shampoos that are marketed as DHT blockers.
These products contain active ingredients that wash away excess DHT from your scalp, which may help protect against hair loss.
Another is ketoconazole — a topical antifungal medication linked to improvements in hair growth in men, but isn’t directly linked to lower DHT levels.
Hair growth shampoos aren’t as effective as medications like finasteride, so they’re best used as one part of your hair care routine, not on their own.
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Most men don’t experience any side effects from DHT blockers — unless you consider noticing thicker, fuller and healthier hair a side effect, of course.
However, a small percentage of men who use DHT blockers like finasteride do experience some side effects. These can range from a mild increase in your testosterone levels to sexual function issues such as erectile dysfunction (ED) and a reduced sex drive.
Higher testosterone levels. Because DHT blockers like finasteride stop the conversion of testosterone to DHT, they may contribute to a slight increase in your total testosterone levels.
In a study published in the journal Urology in 2003, researchers found that long-term use of finasteride was associated with a modest increase in testosterone.
Lower sex drive. Most of the time, finasteride has no positive or negative effect on your sex drive. While taking it, you’ll feel the same as normal. However, in a small number of men, finasteride can result in a noticeably reduced level of interest in sex.
Weak erections. Just like reduced sex drive, this is a rare side effect that affects a small number of finasteride users. Some men report getting less “morning wood” while using finasteride, possibly due to lower levels of DHT.
While the side effects listed above might seem off-putting, the reality is that the vast majority of men that use DHT blockers such as finasteride don’t get serious side effects.
To put things in perspective, a 2012 study of finasteride in Japanese men found that out of the 3,177 men who used finasteride, only 23 developed adverse reactions. Even at five times the regular dosage for preventing hair loss, side effects from finasteride are rarely reported.
It’s also worth noting that in the rare event of sexual side effects occurring, they’ll almost always stop once you stop taking finasteride. It’s very uncommon for any negative effects to continue if you don’t actively take a DHT blocker.
Early in your life, DHT plays a critical role in your physical development. If you have low levels of DHT, you may be diagnosed with a condition called 5-alpha reductase deficiency.
5-alpha reductase deficiency is a serious condition, and it can affect your genital development, sexual identity and appearance. Many men with 5-alpha reductase deficiency have genitalia that appears female, or isn’t distinctly male or female in its appearance.
Although low levels of DHT can have a huge impact on your health and physical development early in your life, DHT isn’t so important when you’re an adult.
In fact, research generally suggests that as an adult, DHT doesn’t play a significant role in your physiology.
Put simply, the evidence we have right now doesn’t suggest that you can have overly low DHT levels by using medication like finasteride.
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DHT plays a major role in male pattern baldness. It’s the hormone responsible for that receding hairline you’re starting to notice, as well as other common signs of hair loss like a bald patch at your crown or diffuse thinning on your scalp.
If you’re starting to notice male pattern baldness, reducing your DHT levels is the most effective way to slow down, stop or reverse your hair loss.
If you’re not sure where to start when it comes to blocking DHT, keep the following in mind:
Finasteride is your most effective option for reducing DHT levels. This medication blocks DHT at its source by inhibiting the enzyme that creates it. Finasteride is easy to use and can be taken once a day to lower your DHT production.
DHT-blocking shampoo is also helpful. Look for active ingredients like saw palmetto, which may block DHT at the scalp level. DHT-blocking shampoo is most effective when it’s used with finasteride.
Other non-DHT treatments can also help with hair loss. For example, the medication minoxidil works by stimulating hair growth at your scalp level, making it a great choice for use with finasteride and DHT-blocking shampoo.
Interested in getting started? Take part in a hair loss consultation to learn more about your best options for preventing hair loss, stimulating hair growth and maintaining a fuller, thicker head of hair throughout your life.
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Dr. Knox Beasley is a board certified dermatologist specializing in hair loss. He completed his undergraduate studies at the United States Military Academy at West Point, NY, and subsequently attended medical school at Tulane University School of Medicine in New Orleans, LA.
Dr. Beasley first began doing telemedicine during his dermatology residency in 2013 with the military, helping to diagnose dermatologic conditions in soldiers all over the world.
Originally from Nashville, TN, Dr. Beasley currently lives in North Carolina and enjoys spending time outdoors (with sunscreen of course) with his wife and two children in his spare time.
Bachelor of Science, Life Sciences. United States Military Academy.
Doctor of Medicine. Tulane University School of Medicine
Dermatology Residency. San Antonio Uniformed Services Health Education Consortium
Board Certified. American Board of Dermatology
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