Hair Loss Disorders Alopecia
Hair disorders include excessive hairiness (hirsutism), hair loss, and ingrown beard hairs. Although most hair disorders are not serious or life threatening, they are often perceived as major cosmetic issues that require treatment.
Different people have widely varying amounts of body hair. A person’s age, sex, racial and ethnic origin, and hereditary factors determine the amount of body hair. The definition of “excessive” hair is subjective. In some cultures, hairy men are considered masculine; in others, hairiness is eschewed. Some women detest having any body hair, whereas others are not concerned by it. Rarely, excessive hairiness is present at birth (because of a hereditary disorder) but usually develops later in life. In women and children, excessive hairiness can be caused by disorders of the pituitary gland, adrenal glands, or ovaries that result in overproduction of male hormones.
Hair loss may develop gradually or suddenly. It results from hereditary factors, aging, local skin conditions, and diseases that affect the body generally (systemic diseases). Many different drugs can also cause hair loss. When it occurs on the head, hair loss is generally referred to as baldness.
Androgenetic alopecia is the most common type of hair loss, eventually affecting about half of all men (male-pattern baldness) and 10 to 20% of women (female-pattern baldness). A slightly elevated level of the male hormone dihydrotestosterone probably plays a major role, along with genetic factors. The hair loss can begin at any age, even during the teenage years.
Toxic alopecia is hair loss resulting from physical or psychologic stress. Sudden weight loss, many severe illnesses (particularly those that involve a high fever), or surgery may cause hair loss. Some drugs—including chemotherapy drugs, blood pressure drugs, oral contraceptives, vitamin A, and retinoids—can also cause the condition. Toxic alopecia may also result from an underactive thyroid gland or pituitary gland and commonly occurs after pregnancy.
Alopecia areata is a common skin disorder in which round, irregular patches of hair are suddenly lost. The cause is believed to be an autoimmune reaction, in which the body’s immune defenses mistakenly attack the hair follicles. The site of hair loss is usually the scalp or beard. Rarely, all body hair is lost, a condition called alopecia universalis. Alopecia areata occurs in both sexes and at all ages but is most common in children and young adults. Alopecia areata is not the result of another disease, although some people also have a thyroid disorder. The hair usually grows back in several months. In people with widespread hair loss, regrowth is unlikely.