Androgenetic alopecia is a type of hair loss that is inherited from either or both the mother and the father. Also known as male- or female-pattern hair loss, it is the most common cause of hair loss.
The condition occurs when the growth (anagen) phase of the hair growth cycle becomes shorter and shorter. A genetic sensitivity to androgens, a type of hormone, causes hair follicles—where hair growth begins—to sprout hairs that are thinner than normal. The hairs become thinner and thinner, and eventually the follicles die away.
In men, hair loss occurs on the front hairline and forehead and on the top of the head. Bald spots are noticeable.
In women, hair loss occurs as thinning of hair on the top of the head. Women tend to keep their front hairline and do not generally develop bald spots.