It's common for both men and women to lose hair or experience thinning hair as they near middle age. But sometimes hair loss - either temporary or permanent - can occur at younger ages.
According to the American Academy of Family Physicians, temporary hair loss may be caused by stress triggered by serious illness, for example.
Hair loss may also be attributed to hormonal changes or imbalances, such as an over- or under-active thyroid, or pregnancy.
Correcting these hormonal imbalances can restore hair growth. Hair loss also can be triggered by certain medicines like blood thinners, drugs that treat cancer, an excess of vitamin A, medicines for gout, some birth control pills, and antidepressants.
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These types of hair loss are usually temporary. Damage to the hair, caused by styling that pulls or chemically treats the hair, may cause a type of hair loss called alopecia. In these cases, hair loss may be permanent if the hair follicles are damaged.