DHT and hair loss: how the hormone drives hereditary hair loss

Behind hereditary hair loss is a hormone: dihydrotestosterone, or DHT for short. It is formed in the body from testosterone and, in people with the corresponding predisposition, gradually causes the hair follicles at the forehead and crown to shrink. The hairs become finer and shorter until they stop growing altogether. It is precisely this link that explains why many treatments lower the DHT level.

One important point up front: DHT is not a “bad” hormone, but a normal messenger with important roles in the body. It only becomes a problem at hair follicles that are hereditarily sensitive to it. Whether a DHT-lowering treatment is an option for you is determined by a medical review. With us, that happens without a long wait.

What is DHT?

DHT belongs to the androgens, the male sex hormones. It is not produced directly, but is formed from testosterone in the tissue. This is the job of the enzyme 5-alpha-reductase, which converts testosterone into the more potent DHT.¹

At the androgen receptor, the docking site in the cell, DHT is considerably more potent than testosterone. It binds about twice as tightly and detaches again around five times more slowly.¹ As a result, it has a stronger and longer-lasting effect on sensitive tissues, including the hair follicle.

5-alpha-reductase occurs in two main forms, which DHT blockers inhibit to differing degrees. Type I is found mainly in the skin, for example in the sebaceous glands. Type II is active in the prostate and genital tract, but also occurs at the hair follicle, and it is precisely this type that the active ingredient finasteride primarily inhibits.¹

DHT performs regular functions in the body:

• Before birth: It controls the development of the external male genitalia.
• During and after puberty: It is involved in body and facial hair as well as sebum production.
• In adulthood: It contributes to the growth of the prostate.¹

Switching it off completely would therefore be neither possible nor sensible. In hair loss, the aim is only to dampen its influence on the scalp.

How DHT triggers hair loss

Every scalp hair repeatedly goes through a cycle of a long growth phase (anagen), a short transitional phase and a resting phase, at the end of which the hair falls out and a new one grows back. In genetically sensitive follicles, DHT interferes with this rhythm: via the androgen receptor it shortens the growth phase and sets off what is known as miniaturisation.²

Miniaturisation means that the follicle becomes smaller and smaller over several cycles. With each pass it produces a finer, shorter and less pigmented hair, until in the end hardly any visible hair remains. In the affected areas of the scalp, hereditary hair loss shows more 5-alpha-reductase, more androgen receptors and more DHT than in unaffected areas.² The process runs slowly over years, which explains why the temples and the crown often thin out gradually.

The typical pattern is striking. Affected above all are the forehead, the receding hairline at the temples and the crown, while the rim of hair at the back and sides usually remains intact. The reason is the differing sensitivity of the follicles and not the amount of DHT at the particular spot. Clinical observation shows that the hair roots at the back of the head barely respond to DHT and therefore remain stable; exactly why this is so has not yet been conclusively clarified. Hair transplantation is also based on this observation, transplanting resistant hairs to the front. How this pattern differs from other forms of hair loss is placed in a broader context in the article Understanding hair loss.

Why are some people affected and others not?

What is decisive is how strongly the hair follicles respond to DHT, not how much DHT someone produces. Two men with a similar hormone level can have completely different hair density, because their androgen receptors respond to differing degrees. This predisposition is hereditary.²

The predisposition is inherited polygenically, so several genes are involved, and from both the maternal and the paternal side.² The widespread idea that the maternal grandfather alone is decisive therefore falls short. The predisposition can come from both parents, and how strongly it shows varies from person to person. So the family picture can indicate a tendency, but no guarantee in one direction or the other.

What DHT blockers are

DHT blockers in the medical sense are 5-alpha-reductase inhibitors. They block the enzyme that converts testosterone into DHT and thereby lower the DHT level.³ Less DHT means less pressure on the susceptible follicles, which slows the miniaturisation and can allow affected hair roots to stabilise.

Two active ingredients are mainly in use, and they differ in their approval status:

• Finasteride: For the treatment of hereditary hair loss in men, it is approved in Germany and well studied. How it works in detail and which side effects are possible, you can read in the article Finasteride: effects and side effects.
• Dutasteride: For hair loss it is not approved in Germany and is therefore only used off-label, usually when finasteride is not sufficient. It inhibits both types of 5-alpha-reductase and is therefore more potent. Whether and in what form it is an option is always decided by a doctor after weighing up the individual case; we deliberately do not state a dosage here. What the off-label status means in practice is explained in the article Switching from finasteride to dutasteride.

5-alpha-reductase inhibitors are contraindicated in pregnancy and for women of childbearing age, because they can disrupt the genital development of a male foetus. The medical review covers this as well.

What “natural DHT blockers” can really do

Alongside the medications, various herbal products are marketed as “natural DHT blockers”. The name that comes up most often is saw palmetto. Its extract is discussed as a partial inhibitor of 5-alpha-reductase, so in principle it acts similarly to the medications, only more weakly.

The evidence on this is limited. A systematic review found indications of a possible benefit, but expressly emphasised that robust, high-quality data are lacking and that larger studies are needed.⁴ Saw palmetto is therefore not a proven substitute for an approved drug therapy. The same applies to other over-the-counter approaches such as caffeine-containing shampoos: the evidence for a real effect on hereditary hair loss is weak.

Put honestly, this means: if you want to act against hereditary hair loss in a demonstrably effective way, there is hardly any way around the medically supervised options. We make no promise of efficacy for herbal products, and certainly no purchase recommendation. Anyone who wants to try such preparations should not see them as a substitute for a medical assessment.

When lowering DHT does not help

DHT is the driver of hereditary hair loss, but not every kind of hair loss is hormonally caused. Lowering the DHT level only helps with the androgen-driven pattern, that is, androgenetic alopecia. With other causes, a DHT blocker comes to nothing.

This applies above all to diffuse hair loss, in which the hair becomes thinner evenly across the whole head. Here the triggers are often stress, an illness, hormonal changes or a nutrient deficiency, not DHT. How stress-related hair loss develops and why it usually resolves on its own is described in the article Hair loss due to stress. Often several causes overlap, which is one of the questions that a medical assessment resolves.

Whether a DHT-lowering therapy suits you

Whether your hair loss is hormonally caused at all, and whether a DHT-lowering treatment is medically suitable for you, cannot be read off from your hormone level. That belongs in medical hands. With us, you first answer a medical questionnaire about your hair loss and your health. Our doctors review your answers and decide whether and which treatment is an option.

A prescription is never guaranteed in this, because at the start stands the medical review, not the medication. If a treatment is suitable, we coordinate the further steps and support you medically along the way. An overview of the possible paths is given on the page Therapies.