Androgenic alopecia

Androgenic alopecia, why are we losing our hair?

The Norwood Hamilton scale measures the different steps of your alopecia.

How to identify your type of hair loss?

The origin of the androgenetic alopecia, the most common pathology, still has unknown or unclear explanation. It clearly shows the insufficiency of the medical treatments offered in order to stop the evolution of alopecia. Besides those treatments cannot induce a new hair growth cycle.

For men, the culprit of hair loss would be the DHT (dihydrotestosterone) or a testosterone derivative under the action of the 5a reductase (several types exist including the type 1 and the type 2).

This DHT causes a decrease of the hair growth cycle. The hair growth cycle is divided into different stages ensuing all of our life.

Each stage begins with a hair growth, known as anagen, while we notice our hair grows. This stage lasts several years, 4 years more or less. Then our hair enters in a new stage known as catagen, shorter than the one mentioned earlier. During the catagen phase which lasts between 3 and 4 weeks, the hair dies. Directly following the catagen stage follows the telogen stage where the follicle bulb comes closer to the skin surface area, climbing through the hair sheath. This cycle last phase ends with the telogen stage where the hair bulb is expelled.

Each hair follicle has its independent growth rhythm; otherwise all our hair will fall out at once and we will be entirely bald for months. A complete hair growth cycle lasts between 4 and 5 years for men. The hair growth cycle rules are slightly different for women; it lasts between 6 and 7 years. Another stage of the hair growth cycle exists: the kenogen stage. The kenogen stage represents the intermediary time where the bulb is expelled and where the new growth is beginning. The stage becomes longer and longer in androgenic alopecia.

What is happening?

All along the hair sheath we notice stem cells reservoirs, one is located on the top of the sheath and the other is located under the hair bulb. Those stem cells reservoirs have been identified with the help of stem cells indicators. For men, this indicator is known as the CD200 indicator and we can observe its strong presence in the superior stem cells reservoir. Inside the stem cells inferior reservoir, we can notice the presence of another stem cells indicator, the CD34 indicator.

When the bulb gets closer to the skin surface in the telogen stage, the stem cells reservoirs get closer from each other in order to fusion. The moment they get in contact with the inferior part of the epidermis, we can clearly see a migration of the stem cells population deeper in the skin in order to form a new hair bulb. This phenomenon is not properly complete during the different phases of the alopecia where we observe the miniaturization of the follicles and a characteristic hair loss.

During the androgenic alopecia, the CD34 disappears and the kenogen stage increases. Growing old the presence of the CD34 declines in the inferior reservoir.

Androgenic alopecia