What causes Male Pattern Hair Loss (aka. Androgenic Alopecia)?

Male Pattern Hair Loss (MPHL) is a common condition affecting half of all men by the time they reach the age of 50.

So what is the cause of male pattern hair loss?

Let’s look at the two main culprits responsible for this:

Genes

Hair loss due to MPHL occurs only if a person has a specific genetic code in his or her chromosomes. This code responsible for baldness is carried by a single gene or a group of genes and may be inherited from either mother or father.

However, it is important point to note that not everyone who carries the genes responsible for MPHL will develop baldness.

To be active, the gene for baldness has to be “expressed” in the individual. The expression of a particular gene or genes depends on several factors such as hormones, age, stress level and so on.

Thus, if a person does not develop male pattern baldness, the reason can be either the absence of this gene or lack of its expression.

A family history of MPHL on either side of the family is seen in around 80% while in 20% of cases, there is no family history.

Hormones

Two types of male hormones (androgens) are involved in the mechanism of male pattern hair loss. These are Testosterone and Dihydrotestosterone (DHT). Dihydrotestosterone is a derivative of testosterone.

The relationship of Male Pattern hair loss with testosterone levels was observed by Hippocrates, who noticed that young male eunuchs (castrated male) did not develop hair loss . This is because they had no testosterone to convert to DHT.

In the body Testosterone is converted to DHT (Dihydro-testosterone) by an enzyme (5-alpha reductase). DHT acts on different organs in the body including the hair follicles and cells in the prostate. We can verify the importance of this enzyme in MPHL as it does not occur in men with a genetic deficiency of 5-a reductase, thus resulting in no formation for DHT.

Genetics somehow affects the hair follicles making them more “sensitive” to DHT leading to weaker shorter hair.

The result of this is “miniaturisation” of the hair follicle. Eventually the hair follicle closes up and hair stops growing completely.

Balding hair gradually changes from long, thick, coarse, pigmented hair into fine, unpigmented vellus sprouts (fine hair)

In addition to the hair follicle miniaturization that leads to thin hair fibres in MPHL, a reduction in anagen  (growth phase) duration leads to shorter hair length, while an increase in telogen (resting phase) duration delays regeneration. This results in hairs so short and fine that they fail to achieve sufficient length to reach the surface of the scalp.

At the same time the sebaceous gland attached to the follicle remains the same size. As the hair shafts become smaller, the gland continues to pump out about the same amount of oil. So as your hair thins, you will notice that your hair becomes flatter and oilier.

It is not clear why different hair follicles are affected at different times, making the balding process gradual, or why only hair on the scalp is affected.

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