Why do some women lose their hair?

Dr. Mehmet Oz, MD
Cardiology (Cardiovascular Disease)

It's normal to find shed hair in your hairbrush or on your sweater -- but excess hair loss can be a sign of trouble. In this video, Dr. Oz helps you tell the difference, and discusses the problems that may be behind your thinning scalp. 

Dr. Jack Merendino, MD
Endocrinology Diabetes & Metabolism
Most people do not realize how common hair loss is in women. But there are plenty of women out there, especially older women, who have lost so much hair they choose to wear a wig or otherwise hide the problem.

Roughly speaking, hair loss-also called alopecia-is divided into two main causes: hormonal and non-hormonal. Non-hormonal hair loss results from many problems. Nutritional deficiencies, such as in women who have lost a tremendous amount of weight rapidly from a major illness, following gastric bypass surgery or with severely calorie-restricted diets, can lead to significant hair loss. Specific vitamin or mineral deficiencies can lead to hair loss. Medications, such as chemotherapy drugs, may be toxic to hair follicles and cause alopecia. A common cause of hair loss is alopecia areata, an immune-mediated problem that usually causes patchy hair loss. This condition responds well to corticosteroid treatment. Major emotional stress will also often cause hair loss, sometimes quite severe. Again, the hair will usually return, but the hair loss itself only adds to the anxiety or depression that the woman is feeling.

There are two main causes of hormone-related hair loss. The first is hypothyroidism, or an under-active thyroid. Treatment of the thyroid problem usually results in the return of lost hair.

By far the most common hormone-related cause of hair loss in women is the same as in men: dihydrotestosterone, or DHT, a major metabolite of the primary male hormone testosterone. Both men and women produce DHT, and in a person with the genetic predisposition, DHT exposure leads to hair loss on the scalp. Because hair loss of this type depends both on a male hormone, or androgen, and on genetics, it is termed “androgenetic alopecia.” Women who have androgenetic alopecia lose their hair more slowly than men because their levels of DHT are lower. Medications that block testosterone, such as spironolactone (Aldactone), can be used to block the effects of male hormones in women. Prescription drugs that block DHT, such as finasteride (Proscar or Propecia) or dutasteride (Avodart) work on hair loss in men and theoretically should help women. However, these drugs have not been approved by the Food and Drug Administration for use in women and are potentially dangerous in a woman who might become pregnant because they can interfere with the sexual development of the fetus.

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