It is a hormone that stimulates the development of male characteristics (an androgen). It is made through the conversion of testosterone.
Every day, almost 10% of the testosterone produced by an adult is converted to dihydrotestosterone by the testes and prostate (in men), the ovaries (in women), the skin, and other parts of the body.
However, this figure is much lower before puberty. It is believed that the increased production of dihydrotestosterone may be responsible for the onset of puberty in boys, causing the development of the genitalia (penis, testicles, and scrotum) and growth of the pubic and body hair.
This hormone also causes the prostate to grow and is believed to combine with testosterone, inducing the expression of male sexual behavior.
Dihydrotestosterone is often more potent than testosterone, and many of the effects that testosterone has on the body only occur after it is converted to dihydrotestosterone.
Less is known about the importance of dihydrotestosterone in women. Still, it is known to cause much of the growth of body and body hair in girls after puberty and can help determine the age at which girls begin puberty.
How is dihydrotestosterone controlled?
The amount of dihydrotestosterone present in the body from one day to the next depends on the amount of testosterone present.
When testosterone levels increase, more of it is converted to dihydrotestosterone, and therefore dihydrotestosterone levels also increase.
Therefore, the control of dihydrotestosterone levels in the body is achieved through the power of testosterone production, which is controlled by the hypothalamus and the pituitary gland.
In response to the decrease in testosterone levels (and thus to the reduction of dihydrotestosterone), the hypothalamus releases the hormone gonadotropin, which travels to the pituitary gland and stimulates it to produce and release a luteinizing hormone into the bloodstream.
Luteinizing hormone in the blood travels to the Leydig cells in the testes of men (or the ovaries in women) and stimulates them to produce more testosterone.
As testosterone increases in the blood, more of it is also converted to dihydrotestosterone, resulting in higher levels of dihydrotestosterone.
As blood levels of testosterone and dihydrotestosterone rise, they feedback to suppress gonadotropin-releasing hormone production from the hypothalamus, which suppresses luteinizing hormone production by the pituitary gland.
Testosterone (and therefore dihydrotestosterone) levels begin to decline. As a result, negative feedback decreases, and the hypothalamus resumes secretion of the releasing hormone gonadotropin.
What if I have too much?
Too much dihydrotestosterone, often due to excess testosterone production, has variable effects in men and women. Dihydrotestosterone levels are unlikely to rise before the onset of puberty.
Adult men with too much dihydrotestosterone are also unlikely to experience recognizable changes.
Women with too much dihydrotestosterone may develop increased growth of body, facial, and pubic hair (called hirsutism), interrupted menstrual periods (amenorrhea) and increased acne.
Abnormal changes in the genitals can also occur in women with too much dihydrotestosterone.
What if I have too little dihydrotestosterone?
Dihydrotestosterone is believed to have a more negligible effect on women, and as a result, they are thought to be relatively unaffected by having too little dihydrotestosterone.
However, the onset of puberty may be delayed in girls with too little dihydrotestosterone, and the amount of pubic and body hair present in adult women may also be reduced.
In contrast, low levels of dihydrotestosterone in men can have dramatic effects.
If there is too little dihydrotestosterone while male fetuses are still in the womb, for example, they may not “masculinize,” and their genitalia may appear similar to those seen in girls of the same age.
Later, boys with too little dihydrotestosterone may experience changes usually seen at puberty (such as muscle growth and sperm production) but will not develop average body hair growth and genital development.
Hair growth and hair loss
Male pattern hair loss is the most common type of hair loss in men. The hair at the temples and the crown slowly thin out and eventually disappears.
The exact reason this happens is unknown, but genetic, hormonal, and environmental factors are believed to play a role. The DHT hormone is believed to be an essential factor.
Three phases of hair growth
To understand male pattern hair loss, we must understand hair growth.
Hair growth is divided into three phases:
- Anagen: it is the growth phase. The hairs remain in this phase for 2 to 6 years. The longer it lasts, the longer the hair grows. Usually, about 80 to 85 percent of the hairs on the head are in this phase.
- Catagen lasts only two weeks. It allows the hair follicle to renew itself.
- Telogen: it is the resting phase. The follicle remains inactive for 1 to 4 months. Usually, between 12 and 20 percent of the hairs are in this phase.
After this, the anagen phase begins again. New growth pushes existing hair out of the pore and sheds naturally.
Male pattern hair loss occurs when the follicles slowly miniaturize, the anagen phase shortens, and the telogen phase lengthens.
The shortened growth phase means that the hair cannot grow as long as it used to.
Over time, the anagen phase becomes so short that the new hair does not even peek through the skin’s surface. The growth of telogen hair is less anchored to the scalp, which facilitates its fall.
As the follicles get smaller, the hair shaft gets thinner with each growth cycle. Over time, the hairs shrink into fuzzies, the kind of soft, light hairs that coat a baby and mostly disappear during puberty in response to androgens.
Anabolic steroid users, including bodybuilders, have higher levels of DHT. However, they often experience hair loss.
Hair on the head grows without the presence of DHT, but underarm hair, pubic hair, and beard hair cannot succeed without androgens.
People who have been neutered or deficient in 5-AR do not experience male pattern baldness, but they will have very little hair on other body parts.
For reasons that are not well understood, DHT is essential for most hair growth, but it is detrimental to hair growth on the head.
DHT is believed to bind to androgen receptors in hair follicles. An unknown mechanism appears to activate the receptors to begin miniaturizing.
Why does DHT affect people in different ways?
DHT affects people in different ways. This can be due to:
- An increase in DHT receptors in the follicle.
- An increase in local DHT production.
- Increased sensitivity of the androgen receptor.
- Increased DHT production is produced in other body parts and comes through circulation.
- Increased production of circulating testosterone that acts as a precursor to DHT.