Categorized | Causes

Alopecia: Is testosterone to blame for hair loss?


Hair loss can be induced by many factors, starting with poor diet and ending with genetic predisposition. It can be a purely cosmetic problem and not a permanent one. For example, if hair loss happens seasonally (in November, March or April), it can be associated with hypovitaminosis which can cause a decrease in body defenses. In addition, increased hair loss can develop by contracting an infectious disease, a scalp infection or severe stress. However, in most of the cases, loss of hair is not just an aesthetic defect but can be caused by a serious dermatologic disease – androgenic alopecia (also called androgenetic alopecia, female or male pattern baldness). In this case, cosmetic remedies are useless and a consultation with a dermatologist is required.

Androgenic alopecia is a type of hair loss that is caused by one of the following reasons:

  • Excessive male sex hormone Androgen or dihydrotestosterone (DHT), a more potent form of testosterone;
  • Increased sensitivity of the hair follicles to dihydrotestosterone;
  • Increased activity of the 5α-reductase enzyme that converts testosterone into dihydrotestosterone.

According to some estimates, androgenic alopecia is diagnosed in up to 95% of hair loss cases in males and females. In men, androgenic alopecia starts from the hairline on the forehead and spreads to the crown of the head (although other variants are possible). In women with this form of hair loss, there is a progressive hair thinning almost all over the head, and especially on the crown of the head.

It was Hippocrates who noticed that eunuchs never grew bald. Later, Aristotle noted the same interconnection. And in the 20th century, Dr. James Hamilton wrote that hair loss could be caused by an excess of male sex hormones in combination with genetic predisposition.

Strictly speaking, we cannot say that sex hormones suppress or enhance hair growth. The effects of estrogens (female hormones) and androgens (male hormones) on hair will be determined by the presence of a specific receptor on the surface of the hair follicle cells. This receptor is like a ‘button’, and DHT hormone is like a ‘finger’ that presses this button. The result of this pressing is predetermined by the mechanisms present in the follicle. You may press identical buttons with the same finger and it may result in an explosion, and in another, the launch of a spaceship.

The question is “What wires lead to these buttons?”. Estrogens promote scalp hair growth and suppress the growth of hair on the body and face. Androgens stimulate the growth of beard and mustache, as well as hair growth on some body parts and can inhibit hair growth on the head. Of course, what is important here is not so much the androgens as in the types of follicles and the areas where they are located. If the hair follicles in the scalp that have DHT-dependent ‘buttons’ that stop hair growth then hair will start falling out in response to the increased concentration of androgens. If the hair follicles of the beard and mustache are transplanted to the scalp, then the excess of androgens will cause hair growth on the scalp. One of the treatment options for androgenetic alopecia is in the transplantation of the follicles activated by dihydrotestosterone to the areas of baldness.

Women suffering from androgenic alopecia along with hair loss may also have other signs of hyperandrogenic syndrome – excessive hair growth on the face, acne and oily seborrhea. However, virilization, which is the development of masculine characteristics in body building, is rarely observed. Almost always both men and women who have androgenic alopecia have normal or insignificantly increased concentration of androgens in their blood.

As it has already been said, it is believed that one of the main causes of androgenic alopecia is the increased activity of the 5α-reductase enzyme. This enzyme is present in the human body in two types:

  • -reductase type I is found in the prostate gland in males;
  • -reductase type II – in hair follicles and sebaceous glands.

The main function of this enzyme is to convert testosterone circulating in the blood into its active form – dihydrotestosterone. One may ask “Why do hair follicles convert testosterone into DHT if it causes hair loss?” There is a profound biological reason for this. Hair is an important sexual characteristic, so it has to know on what area of the body to grow. And that depends on whether the sex of the body is male or female. The activity of hair follicles located in the area of the chin, chest, arms and legs is stimulated by DHT (which is a male hormone), and suppressed by female hormones. This is why mustache, beard, hair on legs, arms and other body parts are characteristics for men. High levels of male sex hormones in women also stimulate the activity of the hair follicles in these body parts causing increased hair growth (male pattern of hair distribution). Remember, the activity of the hair follicles located in the scalp is stimulated by estrogens and suppressed by androgens. Female sex hormones stimulate the growth and extend the life cycle of hair on the scalp and at the same time they suppress hair growth on the face and body. This is why long hair is a natural characteristic of women.

Dihydrotestosterone causes the shortening of the growth phase in some hair follicles making them enter the resting phase prematurely. These follicles do not reach their maximum size and start producing thin and weak hair. They become atrophic. Since the ratio between the follicles in the growth phase and those in the resting phase is shifted towards the resting follicles, there appears to be a lot of follicles that discard their hair fibers simultaneously. Therefore, the thinning and weakening of hair result in progressive hair loss. The good news here is that these hair follicles do not die off, so it is possible to restore hair growth.

In addition, the concentration of hormones in the human body is not static. In some men, the level of testosterone drops by 10% every ten years after the age of thirty. The concentration of testosterone in blood reaches its peak in autumn and its minimum in spring. Therefore, for both males and females, hair grows best in spring and falls out predominantly in autumn.


Temporary Alopecia can be provoked by a variety of causes and conditions (stresses, infections, etc.). Among all these factors, hormonal cause is the most common and, in many cases, leads to chronic hair loss in males and females. So should we blame testosterone for the scalp getting balder and balder? Well, technically speaking, it is not testosterone that makes our hair fall out, it is the hair follicles being hypersensitive to it.