The most common cause of hair loss is called male-pattern baldness or female-pattern baldness, which is a hereditary condition, states Mayo Clinic. Hair loss can also be caused by medications, hormonal factors and medical conditions.
Certain hormones trigger particular patterns of permanent hair loss for people who are genetically susceptible, notes Mayo Clinic. Hormonal changes and imbalances can also cause temporary hair loss. These changes can be due to pregnancy, childbirth, discontinuation of birth control and the onset of menopause. For men, thinning hair due to hormonal factors can begin as early as puberty.
Hair loss can also be the result of problems with the thyroid glands, which help regulate hormone levels, states Mayo Clinic. A disease called alopecia areata occurs when the body's immune system attacks hair folicles, causing round patches of hair loss. Ringworm or other scalp infections can cause hair to fall out. Once the infection is treated, the hair usually grows back. Lichen planus and some types of lupus can cause permanent hair loss.
Hair loss can be caused by medications used to treat cancer, depression, arthritis, high blood pressure and heart problems, according to MayoClinic. After a physical or emotional trauma, many people experience a general thinning of hair. Traction hair loss can occur if hair is pulled too tightly in styles such as pigtails or cornrows.