Is Androgenetic Alopecia (AGA) Caused Only By The Effects Of DHT?
Alopecia also referred to as hair loss or hair shedding, is usually associated with an imbalance between hair regrowth and hair loss. A physiological hair loss is defined as a loss of hair that is not exceeding more than 70 to 100 per day. However, this may increase in healthy individuals during seasons like Spring and Autumn. (1) Alopecia may be divided into two forms known as scarring and non-scarring alopecia. While scarring alopecia involves the destruction of hair follicles, non-scarring alopecia does not include hair fall destruction and is associated with other causes. One of the most common causes of non-scarring alopecia is the changes in hormone levels in males and females. This is known as Androgenetic Alopecia. The interaction of the androgen and skin tissues occurs at the hair follicle level, which is also considered the peripheral organ for synthesizing cholesterol and androgens. (2) (3)
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What is DHT?
DHT, which stands for Dihydrotestosterone, is considered the tissue metabolite of the male sex hormone testosterone. This is formed by the enzyme 5 alpha-reductase, which occurs in two isoforms. While one form of this enzyme is found in the outer skin layer known as the epidermis and the sebaceous glands, it may also be found in the hair follicles and sweat glands. (4) On the other hand, the other form of the enzyme is primarily located in the hair follicles. Moreover, the conversion of testosterone to DHT is also caused by this second form of the 5 Alpha Reductase enzyme. (5) DHT is considered three times more effective at binding to the sex hormone-binding globulin than other sex hormones like testosterone. In males, almost 70% of Dihydrotestosterone is formed by conversion from testosterone, while in females, it is formed by conversion of androstenedione.
The levels of DHT are also considered an essential factor in determining the cause of alopecia, mainly in males. Data shows increased levels of DHT can be found in males with Androgenic alopecia and Klinefelter syndrome. However, this association is not only limited to males but may also be observed in females. At least 40% of the women with hirsutism and 35% with PCOS may also have elevated levels of DHT. (6)
What is Androgenic Alopecia?
Androgenic alopecia may be found in both males and females. In males, androgenic alopecia is among the most common hair fall causes. Even though this may be encountered at any age in males, its incidence increases in older men. Statistical data shows that while males aged 25 years may be at a risk of 25% for androgenic alopecia, those aged 40 may be at a risk of 40%. Moreover, males aged 50 may have an even higher risk of 50%. (5)
Androgenic alopecia in females is also among the most common causes of hair fall. Similar to males, the incidence of androgenic alopecia is also seen to increase with the increasing age of females. Data shows that while females aged 29 years may be at a risk of 12%, those aged 49 or under it may be at a higher risk of 25%. Females aged 79 years or more may be at a risk of more than 50% for androgenic alopecia. As females cross, most of the population experience androgenic alopecia, while only 40% may stay protected from this form of hair loss. (7)
The Association of DHT and Androgenic Alopecia
The levels of DHT in males and females have often been linked with Androgenic Alopecia, experienced at different stages of line. DHT binds to specific receptors in the body. The complex formed by this binding can enter the nucleus of hair cells and, as a result, combine with the cell's DNA. This binding to the DNA leads to the activation of specific genes that promote the transformation of healthy hair follicles to miniaturized follicles. The transformation of healthy hair follicles into miniaturized follicles occurs by lengthening the telogen phase and reducing the anagen phase. This leads to hair thinning, which is often associated with the telogen phase of the hair cycle. This causes an increased villus hair ratio, the terminal form of hair related to a thin follicle. (8)
While DHT can increase the reproduction and growth of hair follicles on the chest, face, and genital area, this effect may not be the same for the scalp. Increasing levels of DHT are usually associated with the inhibition of scalp hair growth. The hair loss that this androgen may cause may be episodic or continuous in nature.
Numerous studies have evaluated the association between DHT and androgenic Alopecia. One such study was conducted on 52 males and females with androgenic alopecia. The study results showed a significant rise in the ratio of DHT to testosterone in these individuals. (9) Another study found males diagnosed with Males androgenic alopecia to have significantly higher DHT levels than healthy males. (10)
Similar to males, the studies conducted on females also showed similar results. These women are also found to have higher levels of DHT in their bodies. It has been estimated that every one in four women may encounter female androgenic alopecia, also associated with signs of virilization and higher levels of androgens. (11) However, unlike males, where testosterone is converted to DHT, the female body converts the 4-androstenedione produced in the ovaries or adrenal gland into DHT.
The Bottom Line
DHT, which stands for Dihydrotestosterone, has the most potent androgenic role in the body and is also responsible for androgenic alopecia in males and females. In addition, studies conducted on the association of DHT levels in the body and androgenic alopecia have found this hormone to play a role in the pathogens of androgenic alopecia. However, not all individuals may be at equal risk for hair falls caused by DHT, as certain factors like genetics may make an individual more susceptible.