Hair loss usually develops gradually. It may be patchy or all over (diffuse). Both men and women tend to lose hair thickness and amount as they age. This type of baldness is not usually caused by a disease. It is related to aging, heredity, and changes in the hormones.
Each strand of hair sits in a tiny hole (cavity) in the skin called a follicle. In general, baldness occurs when the hair follicle shrinks over time, resulting in shorter and finer hair. Eventually, the follicle does not grow new hair. The follicles remain alive, which suggests that it is still possible to grow new hair.