Female pattern baldness involves a typical pattern of loss of hair in women, caused by hormones, aging, and genes.

A hair grows from its follicle at an average rate of about 1/2 inch per month. Each hair grows for 2 to 6 years, then rests, and then falls out. A new hair soon begins growing in its place. At any time, about 85% of the hair is growing and 15% is resting.

Baldness occurs when hair falls out but new hair does not grow in its place. The cause of the failure to grow new hair in female pattern baldness is not well understood, but it is associated with genetic predisposition, aging, and levels of endocrine hormones (particularly androgens, the male sex hormones).

Changes in the levels of androgens can affect hair production. For example, after the hormonal changes of menopause, many women find that the hair on the head is thinned, while facial hair is coarser. Although new hair is not produced, follicles remain alive, suggesting the possibility of new hair growth.

Female pattern baldness is usually different from that of male pattern baldness. The hair thins all over the head, but the frontal hairline is maintained. There may be a moderate loss of hair on the crown, but this rarely progresses to total or near baldness as it may in men.

Hair loss can occur in women for reasons other than female pattern baldness, including the following:

• Temporary shedding of hair (telogen effluvium)
• Breaking of hair (from such things as styling treatments and twisting or pulling of hair)
• Patchy areas of total hair loss (alopecia areata -- an immune disorder causing temporary hair loss)
• Medications
• Certain skin diseases
• Hormonal abnormalities
• Iron deficiency
• Underactive thyroid
• Vitamin deficiency

Habif TP. Clinical Dermatology. 4th ed. St. Louis, Mo: Mosby, Inc. 2004:844.

Cummings CW, Flint PW, Haughey BH, et al. Otolaryngology: Head & Neck Surgery. 4th ed. St Louis, Mo; Mosby; 2005:677-679.