- August 11, 2016
- Posted by: emobile
- Category: Trending Topic
Emobileclinic Trending Topic
Dihydrotestosterone (DHT) and male baldness Dihydrotestosterone (DHT) is a sex steroid, meaning it is produced in the gonads. DHT is also an androgen hormone responsible for the biological characteristics that typify males like deep voices, hairy chests and increased muscle mass and so on. It is a multifaceted hormone whose role of DHT is not limited to hair growth but also involves in benign prostatic hyperplasia (enlarged prostate) and prostate cancer too.
Testosterone is converted to DHT by specific enzymes. Roughly 5% of free testosterone is normally converted into DHT. It is a particularly potent androgen, five times more potent than testosterone. It attaches to the same sites as testosterone but with more ease and remains bound for longer periods of time. During fetal development, DHT plays a vital role in the development of the penis and prostate.
Males who are born with 5-AR deficiency have severely underdeveloped prostate and external genitalia, to the extent that some are brought up as girls. Their penis may appear as an enlarged clitoris or be almost totally absent. However, at puberty, some male characteristics, such as hair on the chest and a deepened voice, do appear.
Males with 5-AR deficiency are often infertile.1 As an adult, DHT is the primary androgen in the prostate and hair follicles. Women have no known role for DHT during development. Hair growth and hair loss Male pattern baldness, also known as androgenetic alopecia, is the most common type of baldness in men. Hair at the temples and on the crown will slowly thin and eventually disappear. There is a genetic component to male pattern baldness, and DHT is thought to be one of the major factors involved in its etiology. To understand male pattern baldness, we need to understand hair growth. The following is a brief summary of normal hair growth.
Hair growth is split into three phases: anagen, catagen and telogen: Anagen: the growth phase. Hairs remain in this phase for 2-6 years. The longer this phase lasts, the longer the hair grows. Normally around 85% of the hairs on the head are in this phase Catagen: this phase lasts only 2 weeks and allows the follicle to renew itself Telogen: this is the resting phase where the follicle lies dormant and can last from 1-4 months. Normally 10-15% of hairs are in this phase. Once this phase is over and anagen begins again, the existing hair is pushed out of the pore by the new growth and naturally sheds. In MPB, follicles slowly become miniaturized and the anagen phase of the hairs is reduced.
Due to the shortened growing phase, the hair’s maximum length is reduced. At the same time, the telogen phase lengthens. This cycle slowly becomes more and more weighted toward the telogen phase. Over time, the anagen phase becomes so short that the new hairs do not even peek through the surface of the skin. Added to this, telogen hair growth is less well anchored to the scalp, explaining why there is often hair loss noted during showering. Miniaturization of the follicles causes the shaft of the hair to become thinner and thinner with each cycle of growth.
Eventually, normal (terminal) hairs are reduced to villus hairs. Villus hairs are the soft, light hairs that cover a baby and mostly disappear during puberty in response to androgens. DHT and hair growth Hair on the head continually grows without the presence of DHT. However, hair in the armpit, pubic hair and beard hair cannot grow without the presence of androgens. Interestingly, individuals who have been castrated or have 5-AR deficiency will never suffer from male pattern baldness but will also have very little hair elsewhere on the body.
DHT is entirely necessary for most hair growth but is detrimental to head hair growth. This conundrum is yet to be explained. DHT is thought to attach to androgen receptors on hair follicles and, through an unknown mechanism, genetically trigger the receptors to begin miniaturizing. As evidence for this, researchers have found that both plucked follicles and skin from a balding scalp contain higher levels of DHT than those from a non-balding scalp.
Some scientists believe that male pattern baldness in any specific individual is caused by a genetically transmitted susceptibility to otherwise normal levels of circulating androgens, particularly DHT.
Factors influencing DHT
Science is yet to understand fully why DHT’s effects are greater in some individuals, but there are a number of possible mechanisms at work: Increased DHT receptors at the follicle Increased local DHT production Increased androgen receptor sensitivity Increased DHT being produced elsewhere in the body and arriving through circulation, perhaps via the prostate Increased circulating testosterone that acts as a precursor for DHT.
It is known that DHT binds to follicle receptors five times more avidly than testosterone. However, the amount of DHT in the scalp is tiny compared with the levels in the prostate. How levels are controlled and why they change are not yet understood.