What is male pattern hair loss? The role of DHT and genetics

What is male pattern hair loss?

Male pattern hair loss, known in medicine as androgenetic alopecia, is the most common type of hair loss in men. The name points to the two main factors behind it: androgens (male hormones such as testosterone) and genetic predisposition. “Alopecia” simply means hair loss.

It can start at any age after puberty, and it becomes more common and more noticeable with age. What sets this hair loss apart is that it follows a particular pattern: the hair thins at the temples and the crown, while in most people the hair at the back of the head and on the sides above the ears stays in place.

How does DHT affect the hair root?

Every hair grows from a hair root (follicle). The root works in a cycle: it produces a hair for a while, then rests, sheds the hair and grows a new one. On the scalp, the growth phase (anagen), during which the hair gets longer, can last for years. We describe the phases of this cycle in our article on the hair growth cycle.

An enzyme called 5-alpha reductase converts testosterone into dihydrotestosterone (DHT), a more potent androgen; this conversion also takes place in the hair root itself. DHT binds to hormone receptors (androgen receptors) in the group of cells at the base of the root that controls hair growth (the dermal papilla). If the root is genetically sensitive to this effect, its cycle gradually changes:

• The growth phase gets a little shorter with each cycle; the hair does not grow as long and falls out sooner.
• The root shrinks and produces a finer, shorter, lighter-colored hair. This process is called miniaturization (shrinking of the hair root).
• The resting phase gets longer; it may take longer for a new hair to replace one that has fallen out.

That is why this hair loss is usually noticed not because hair disappears all at once, but because thick hairs are gradually replaced by fine ones. At an advanced stage, the root produces only fine, downy hairs that are hard to see with the naked eye, and over time it may stop producing hair altogether.

Is too much hormone the problem?

Usually not. This hair loss also occurs in men whose blood hormone levels are within the normal range. For the hair loss to develop, androgens and a genetic predisposition are both needed; what matters is how sensitive the roots are to the hormone.

Sensitivity also varies from one area of the scalp to another: in most people, the roots at the back and sides are less sensitive to this effect. Part of this difference has been linked to the roots at the front and the crown having more hormone receptors and more of this enzyme.

What role do genes play?

The tendency to develop this hair loss is largely inherited, but there is no single “baldness gene”; many genes are thought to play a part together. The best known is the androgen receptor gene, which is located on the X chromosome. Because men inherit their X chromosome from their mother, there is a widespread belief that the tendency is passed down only through the mother’s side.

In fact, the genes linked to this tendency are not found only on the X chromosome; the tendency can be passed down from both the mother’s and the father’s side. This hair loss is more common in men whose father or close relatives have noticeable hair loss. Even so, the age at which the hair loss starts and how fast it progresses can differ, even between brothers in the same family.

What do we not know yet?

It is not yet fully understood why the same hormone makes beard hair thicker while shrinking the roots on top of the head. Nor is there a reliable test that shows in advance how fast a person’s hair loss will progress and where it will stop. Genetic tests are being researched, but they are not yet at a stage where they can guide hair transplant planning. Age, family history and examination findings give an idea; they do not allow a definite prediction.

How does the hair loss start and progress?

The hair loss usually progresses over the years, at a rate that varies from person to person. A common course looks like this:

• The hairline recedes at the temples.
• At the crown, thinning begins around the hair whorl; it is often noticed first under bright light.
• The band of hair between the front and the crown thins; in later stages, the two areas may merge.
• At the back and sides, a horseshoe-shaped band of hair running from ear to ear is usually preserved.

Not everyone follows this order. Some men have thinning that spreads across the whole scalp, including the back and sides, without a clear pattern. Because in this case the back and sides, where the grafts would be taken from, can also thin, a hair transplant is often not a suitable option.

In many men, the hairline moves back slightly at the temples after puberty. This is called hairline maturation, and it is not always the start of progressive hair loss. For the classification used to describe the stages, see our article on the Norwood and Ludwig scales.

How is it diagnosed?

Male pattern hair loss is usually diagnosed from your history and an examination. The doctor asks when the hair loss started, how it has progressed and whether anyone in your family has had similar hair loss, and looks at which areas are thinning.

Examining the scalp with a magnifying device (trichoscopy) helps with the diagnosis. In male pattern hair loss, hairs in the same area show clear differences in thickness.

Blood tests are not always needed. If the hair loss is diffuse, has started suddenly or is accompanied by other symptoms, the doctor may order tests. A biopsy (a small tissue sample from the scalp) is usually considered if the picture is unclear.

If your hair is falling out noticeably over a short period or coming out in patches, or if your scalp itches, hurts or is red, see a dermatologist. We do not diagnose from photos or messages.

An overview of treatment options

The aim of medical treatment is usually to slow the hair loss and help shrinking roots keep producing hair. The response to treatment varies from person to person. What follows is general information; your doctor decides which option is right for you.

• Medications that reduce DHT production: These medications (5-alpha reductase inhibitors) reduce the conversion of testosterone into DHT; they are mostly taken by mouth. Finasteride, which belongs to this group, is one of the most studied medications for male pattern hair loss. Side effects such as reduced sex drive, erection problems and mood changes have been reported in some people; if you notice any of these, see your doctor. These medications can also lower PSA, a value checked in prostate screening; if you are going to have this test, tell your doctor that you are taking the medication.
• Medications applied to the scalp: The most studied medication in this group is minoxidil. It is thought to extend the growth phase; how it works is not fully understood. Side effects such as scalp irritation may occur.
• Supporting treatments: There is limited evidence on how well treatments such as PRP (plasma prepared from your own blood) and mesotherapy work in male pattern hair loss.

The effect of these medications can only be judged after several months; when the medication is stopped, the benefit is gradually lost. Do not start these medications on your own or because someone else recommended them. Only your doctor’s assessment can determine whether they are suitable for you, what side effects they may have and how long to use them; also talk to your doctor before you stop or change a treatment.

Does a hair transplant stop hair loss?

No. A hair transplant does not remove the cause of the hair loss; it moves roots that are less sensitive to hair loss to the thinning area. We mostly take the grafts (the groups of roots that are transplanted) from the back and sides of the head, that is, from the donor area. These roots usually keep their lower sensitivity to hair loss in their new place too. We explain this principle in our article on the donor area and donor dominance.

The sensitivity of your own hair around and behind the recipient area, however, does not change; this hair may continue to thin after the transplant. This has several consequences for planning:

• If the hair further back thins, the transition between it and the transplanted area may start to look out of place over time. That is why, when we make the plan, we also take into account areas that may thin in the future.
• The number of roots in the donor area is limited, and a root that is taken is not replaced by a new one; that is why, especially at a young age, we plan to set aside part of the donor area for future needs. We cover this in our article At what age can a hair transplant be done?
• Your doctor may suggest that you consider medical treatment alongside the transplant.
• In the weeks after the procedure, some of the transplanted hair or the hair around it may fall out temporarily; this is called shock loss. Some of the surrounding hairs that had already become thin may not grow back.

What do we look at during the examination?

During the examination, we look at your hair and scalp together and assess, in particular:

• The pattern of your hair loss, the stage it has reached and how fast it has progressed in recent years
• Your age and your family history of hair loss
• The hair density in the donor area, and whether there are signs of thinning there
• Whether any findings suggest another cause for the hair loss

If the cause of the hair loss is unclear, we recommend an assessment by a dermatologist before we discuss a transplant. You can find the different methods on the hair transplant methods page. Whether you are suitable for a hair transplant is determined during the examination, and results vary from person to person.