Hair loss (alopecia) can be caused by various factors, sometimes permanent and sometimes temporary.

Stress, poor eating habits, medication, or certain conditions such as anemia, thyroid disorders, or skin diseases can lead to hair loss.

Androgenetic Alopecia
The most common type of male hair loss is androgenetic alopecia, which accounts for approximately 95% of hair loss cases. It can also occur in women with some variations and in a smaller, though not negligible, percentage.

Unlike other types of hair loss, androgenetic alopecia is not associated with inflammation or scarring.

The onset and progression of this condition are gradual and occur cyclically with periods of flare-ups and remissions. It involves a reduction in both the density and quantity of hair.

Initially, thinning appears in the forehead area, progressing to the front, the upper part, and the top of the scalp. The occipital (back) and parietal (side) regions mostly remain unaffected.

Normal Hair Growth Cycle
An adult has approximately 100,000 to 150,000 hairs, which are renewed at different rates based on the hair growth cycle, which includes three phases:

Anagen Phase (Growth or Regeneration Phase)
This phase lasts 2 to 6 years. The follicles are located deep in the skin, producing thick, brightly colored hairs that grow steadily every day. Normally, at any given time, the largest percentage of hair – approximately 85% – is in this phase.

Catagen Phase (Transition Phase)
This intermediate stage lasts about 2 weeks, during which the hair prepares for apoptosis by shrinking the hair follicles. Approximately 1 to 2% of the hair is in this phase.

Telogen Phase (Rest Phase)
This phase lasts about 3 to 4 months. Hair stops growing until it eventually falls out.

Based on the above cycle, a daily loss of 100 to 150 hairs is considered normal. If this loss is greater and persists over a prolonged period, it is considered hair loss.

Causes of Androgenetic Alopecia
Androgenetic alopecia is caused by a genetically determined increased sensitivity of the hair root to the hormone dihydrotestosterone (DHT), which worsens with aging.

We can therefore identify three main causes associated with this type of hair loss, which are examined in combination and not individually.

Genetic Predisposition – Heredity
Genetic predisposition is a strong factor in the occurrence of androgenetic alopecia, though it is not absolute that every individual with this predisposition will eventually develop the condition.

Although the exact mode of inheritance is unknown, it is certain that the gene responsible for this type of hair loss is inherited from the mother’s side.

Practically, this means that while predisposition can be inherited from both parents, this is certain only if there is a maternal history.

However, even if an individual with a genetic predisposition develops hair loss, the time of onset and rate of progression can vary greatly.

Androgens – The Role of DHT
Androgenetic alopecia occurs due to the effect of the hormone dihydrotestosterone (DHT), a derivative of testosterone, on hair follicles. As a result, the duration of the anagen phase is reduced from 2–6 years to months, even weeks.

This leads to the degeneration of hair follicles, which gradually shrink, producing finer, shorter, and lighter-colored hairs.

It should be noted that high levels of testosterone or other androgens alone are not sufficient to cause hair loss. Hair loss occurs only in combination with high levels of 5-alpha reductase – an enzyme regulating DHT production – and sensitivity to androgen effects, a factor that is inherited.

From the above, it is clear that the combination of androgens and hereditary predisposition ultimately leads to androgenetic alopecia.

Biological Maturation
Naturally, through the process of biological maturation, hair weakens, and hair growth decreases.

Its role in the creation of hair loss lies in the duration during which sensitive hair follicles are exposed to the degenerative effects of androgens.

Consequently, androgenetic alopecia is not a normal result of the aging process, which, however, acts as a catalyst when the two factors coexist.