The most common cause of hair loss is a hereditary condition called male-pattern baldness or female-pattern baldness. It usually occurs gradually and in predictable patterns — characterized by a receding hairline and bald spots in men and thinning hair in women.
Heredity also affects the age at which you begin to lose hair, the rate of hair loss and the extent of baldness. Pattern baldness is most common in men and can begin as early as puberty. This type of hair loss may involve both hair thinning and miniaturization (hair becomes soft, fine and short).