HAIR LOSS IN MEN

Male pattern baldness is the most common type of balding among males. It affects roughly 30% of men by the age of 30, 50% by 50, and 57% by 60. One of the molecules that seems to be intimately linked with male pattern baldness is dihydrotestosterone (DHT). 

What is DHT?
The role of DHT is multifaceted and not solely hair based. It is involved in benign prostatic hyperplasia (enlarged prostate) and prostate cancer too. As such, it is a well-studied and fascinating molecule.
DHT is a sex steroid, meaning it is produced in the gonads. DHT is also an androgen hormone, from the Greek prefix "andro" meaning "masculine."
Androgens are responsible for the biological characteristics that typify males - deep voices, hairy chests and increased muscle mass, for example.
Testosterone is converted to DHT by specific enzymes. Roughly 5% of free testosterone is normally converted into DHT.
DHT 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.
As an example of DHT's vital role in the development of men, this article will briefly mention congenital 5-alpha-reductase (5-AR) deficiency. The enzyme 5-AR converts testosterone into DHT. In this condition, 5-AR is missing.
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. 2
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.3
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.4
 
How DHT affects hair growthHair 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.5
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.5
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.
The role of 5-alpha-reductaseAs mentioned earlier, 5-alpha-reductase (5-AR) is the enzyme responsible for converting testosterone into the much more potent androgen, DHT.
If there is an increase in 5-AR in the body, there will be an increase in the amount of testosterone that is converted into DHT and consequently an increase in hair loss.
There are two versions of 5-AR: type 1 and 2. Type 1 is predominantly found in sebaceous glands that produce the skin's natural lubricant, sebum.
Type 2 5-AR mostly sits within the genitourinary tract and hair follicles. Type 2 is therefore regarded as the more important of the two in the process of hair loss.
The type 2 enzyme and DHT are vital in the formation of a healthy male child in utero, but their effects after birth are thought to be minimal. No processes seem to rely on either.
In the disorder mentioned earlier, 5-AR deficiency, the genitals are not formed correctly. Later in life, however, there are no other discernible consequences of this lack of DHT. Tellingly, individuals with this illness never suffer from male pattern baldness.
Interestingly, the role of type 1 5-AR is still a mystery. Other than its concentration in sebaceous glands, little is known about how it spends its time.
DHT and hair loss medicationMale pattern baldness can have detrimental effects on the overall body image of males. As such, research into products that will curb or, better still, reverse hair loss is ongoing.