The causes of hair loss are plenty including diseases, nutritional deficiencies, hormone imbalances, and even stress. But, one of the most common ones is adrogenetic alopecia.

Alopecia, is in fact, the term for hair loss. Androgenetic is a reference to the fact that factors such as a genetic predisposition to balding and the influence of male hormones-androgens-play a part. There is also a third aspect-aging.

Let's look at these in brief:

Genetics

Genetics is a complicated thing and not easy to understand or predict the behavior of. The case with balding is also the same. Simply the presence (or absence) of balding in one's parents, on either, the mother's or father's side, is not necessarily predictive of one's likelihood of balding. It's very hard to accurately predict who will go bald and how rapidly.

Androgenic Hormones

All normal men and women produce "male" hormones. The most common of these are testosterone, androsteinedione, and dihydrotestosterone (DHT). These hormones are quite important in both sexes, but occur in different concentrations, being much more predominant in males than in females.

This, in part, is responsible for the typical differences between the genders. It is the exposure of the hair follicles to DHT, in a genetically susceptible person, over a period of time, which leads to androgenetic alopecia, or male and female pattern baldness.

Aging

Age and balding are not proportional in any manner imaginable. It is a process and this fact should not be ignored. Like any process, it can be rapid or slow, it can begin toward the end of life or in the late teens, and it can progress in a predictably inexorable fashion, or it can stop and start, seemingly stabilize, and then begin again. But what exactly does happen? Assuming we have a genetically predisposed person, then as the follicles are continuously exposed to DHT, an interesting phenomenon occurs. The anagen phase, or active growth phase of the hair becomes gradually briefer and briefer, and eventually the hair becomes finer and shorter, and less deeply colored.

This is called "miniaturization" of hairs. This is also the point at which hair loss tends to be noticed first. It's not that there are fewer hairs on the head, but that their caliber (cross-sectional area), color and length are so diminished that they no longer provide "coverage" for the scalp beneath.