Male pattern baldness, also known as androgenic alopecia, is a common type of hair loss in men that is related to genetics and male sex hormones. It usually follows a pattern of receding hairline and hair thinning on the crown. The hair loss is progressive, and without treatment, it is permanent. The following factors contribute to male pattern baldness:

• Genetics: Male pattern baldness is related to your genes, and it tends to run in families.
• Male sex hormones: Male pattern baldness is associated with male sex hormones called androgens. Androgens have many functions, including regulating hair growth. With male pattern baldness, the growth cycle of each hair on your head begins to weaken, and the hair follicle shrinks, producing shorter and finer strands of hair. Eventually, the growth cycle for each hair ends, and no new hair grows in its place.
• Age: The chances of developing male pattern baldness increase with age. About 25% of people assigned male at birth see the first signs of hair loss before age 21. By age 50, half experience hair loss, and about 70% will lose hair as they get older.

Male pattern baldness can begin in teenage years, but it more commonly occurs in adult men. Doctors use the pattern of hair loss to diagnose male pattern baldness and may perform a medical history and exam to rule out certain health conditions as the cause, such as fungal conditions of the scalp or nutritional disorders.