Male Pattern Hair Loss

Androgenetic baldness affects at least 50% of men at 50 and around 50% of women at 60. This type of baldness, common to both sexes, therefore affects men about a decade earlier than women. The frequency and severity increase with age , so that at least 80% of Caucasian men show some signs of male pattern baldness at age 70. The prevalence decreases to around 14% in Asian and African population.  
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Hair growth is under complex genetic and hormonal control, mainly regulated by androgens. The androgenic control of hair growth and hair loss in men involves an enzyme: 5-alpha reductase.

 

 It is difficult to understand the mechanism of hair loss in men without understanding the role of this enzyme, 5-alpha reductase. This is the enzyme that transforms testosterone into its more active form, dihydrotestosterone. Dihydrotestosterone is considered to be the most potent androgen affecting the cycle of hair growth in men.

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Dihydrotestosterone has 10 times more affinity for androgen receptors compared to testosterone. It binds to these receptors at the level of hair follicles which are genetically predisposed to fall and alters the cycle of them.

 

Men who suffer from male pattern hair loss have an increased activity of the enzyme 5-alpha reductase in their hair follicles and the male bald scalp has an increased ability to convert testosterone to dihydrotestosterone.

 

Human androgenetic alopecia is characterized by a reduction in the anagen phase and an increase in the telogen phase, leading to a gradual miniaturization of hair follicles. As a result, terminal hair transform into vellus hair decreasing the hair density.

 

Hair follicles in the frontal and vertex regions of the scalp respond to androgens by a reduced length of the anagen phase in genetically predisposed men. Thus, the vigor of the follicles decreases, the hair in these areas become thinner and less dense.

 

It has been proved that the density of androgen receptors in men with androgenetic alopecia is higher at the frontal area than at the occipital area. This is the reason why male pattern balding usually begins in the frontal region.

 

Studies show that the number of hair follicles in normal adults is an average 326 follicles per cm2 and in men with androgenetic baldness the number is 278 follicles per cm2.

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In the 1950s, Hamilton made a classification of male pattern baldness and a few years later, Norwood updated it. Currently, male pattern baldness is classified according to the Norwood - Hamilton scale (see diagram below). Patients are offered medical treatment or a hair transplant based on this classification. It is also used by surgeons to plan the number of grafts to be planned as well as hair distribution in the balding area.