Usually when people think about the subject of hair loss, they tend to just have men in mind. However, there are plenty of women who suffer from premature hair loss too, and some experts estimate that as many as 1 in 4 women will experience hair loss at some time in their lives.
This figure may surprise you but there are several reasons why we don’t notice large numbers of women suffering from premature hair loss. Often they are much better at disguising the condition than men, the hair loss is often less severe than men experience, and the loss is spread more evenly over the head rather than concentrated at the crown, as it is with men.
Causes of female pattern hair loss
In female pattern hair loss women may actually lose hair for some of the same reasons as men. They have a reaction to the male hormones in their body – specifically the conversion of testosterone to dihydrotestosterone (DHT). In female pattern baldness the loss of hair can start later in life than it does in men and the effects are less extreme because women still have the support of estrogen in their body.
Menopause can also contribute towards hair loss because of the changes in hormonal levels, such as the increasing levels of testosterone that are experienced at this time. Sometimes women are prescribed antidepressants for the mood swings associated with the menopause, and these have also been found to sometimes cause hair loss.
Stress and sabotage
Hair loss can also be attributed to a traumatic event that causes stress to interfere with the normal hair growth cycle, triggering a condition known as Telogen effluvium. This is the second most common cause of hair loss in women, but it is reversible as the body adapts to the stress or the stress is relieved. The stress placed on a woman’s body during pregnancy, problems with the thyroid gland, and diabetes are other common causes of Telogen effluvium.
Another type of premature hair loss is Alopecia areata which is a disease of the immune system which causes it to attack the hair follicles, causing healthy hair to fall out in small, round patches all over the head. Some physicians think it may also be a result of a deficiency in the immune system, since in many cases the hair does often re-grow spontaneously.
Researchers have theorized that this type of hair loss may be the result of nutritional deficiencies that cause a shortage of proteins such as iron (serum ferritin). Women who have experienced regrowth without having had any treatment may have inadvertently corrected the nutritional problem without realizing it.
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:
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:
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.