Genetics And Female Pattern Baldness

By Author: Naomi Mannino
Total Articles: 89
Comment this article

Genetics Is What Causes Female Pattern Baldness In Women

Female pattern baldness is much less predictable than male pattern hair loss, and recent research has shown the genetics and mechanisms to be different.

For women, genetic hair thinning, also called androgenetic alopecia, androgenic alopecia, or female pattern baldness, is the most common form of age-related hair loss. In their recent paper "Update on Pathogenesis, Genetics and Medical Treatments of Patterned Hair Loss," published in the November 2010 issue of Journal of Drugs in Dermatology, coauthors Dr. Eric Schweiger and Dr. Robert Bernstein reviewed the major advances in the genetics of women's hair loss over the past decade, as well as our understanding of how it is caused.

Female pattern hair loss is estimated to affect 21 million women worldwide, most commonly older women. By age 20-30, only 6-12 percent of women experience female pattern hair loss, but by age 70, 40-55 percent of women experience some type of hair thinning. Female pattern hair loss in ...
... women increases with age and occurs when more hairs fall out than are replaced by regrowth, although the pattern of thinning is more diffuse (occurring all over the head with no general pattern) than the pattern in men.

Female pattern baldness is caused by three factors: genes, hormones & age

It was believed that female pattern hair loss was caused by the same mechanism as male pattern baldness, but recent studies have shown some differences. While women do experience higher levels of the male hormone (androgen) testosterone in the blood stream as they age and estrogen decreases during menopause, testosterone does not convert to the follicle-attacking dihydrotestosterone (DHT), suggesting that the type II 5-alpha-reductase, which commonly occurs in men and increases as they age, is not as important in female pattern hair loss.

Other research has shown that women may have less 5-alpha-reductase than men but higher levels of the enzyme aromatase, especially at their frontal hairline. Aromatase is responsible for the formation of the female hormones estrone and estradiol, which are thought to decrease DHT formation. This may help to explain why the presentation of hair loss in women is so different than in men, particularly with respect to the preservation of the frontal hairline. It may also explain why women have a poor response to the drug finasteride (band name Propecia), a medication widely used to treat hair loss in men that works by blocking the formation of DHT. Androgens do affect the hair growth cycle in women, but the exact mechanism is still unclear. At this point, according to Dr. Schweiger, female pattern hair loss is multifactorial and a genetically determined trait with both hormonal and nonhormonal causes.

Clinically, female pattern hair loss presents as a diffuse reduction in hair density affecting the crown and frontal scalp, as shown in the Ludwig Scale system of classification. As in male pattern hair loss, there is an alteration of the hair cycle with a gradual reduction in the duration of the growth phase (anagen) and an increase in the telogen phase between the time a hair is shed and the time a new one grows. Studies show the increase in the telogen phase is parallel to the increase in vellus (very fine) hair production and progressive hair follicle shrinkage. As age and pattern hair loss progress, the number of vellus hairs increases and the follicles continue to shrink, until the hair does not grow back and is lost.

The review also found that women with fewer of a particular variant, in the androgen receptor (AR) gene were shown to have an increased risk of developing this type of female pattern hair loss. In women, the AR gene is located on the X chromosome and contains a region encoded by CAG repeats. Research has found that there is an inverse relationship between the number of repeats and AR activity. "If you have fewer CAG repeats, a ‘shorter' gene than most people, then you have a higher risk of developing androgenic alopecia," said Dr. Schweiger.

The number of CAG repeats has also been shown to have clinical implications for disease in women such as polycystic ovarian syndrome, hirsutism (excess facial hair) and acne.

The diagnosis of androgenetic alopecia, or female pattern hair loss

The diagnosis of female pattern hair loss is relatively straightforward when there is a gradual hair thinning in the front and/or top of the scalp, relative preservation of the frontal hairline, a positive family history of hair loss and the presence of miniaturization, which can be observed using a densitometer, a handheld instrument that magnifies a small area of the scalp where the hair has been clipped to about 1 millimeter in length.

When the diagnosis of androgenetic alopecia is still uncertain, further diagnostic information can be obtained from a hair-pull test, a scraping and culture for fungus, a microscopic examination of the hair bulb and shaft, and a scalp biopsy. A dermatologic consultation is warranted whenever the cause of hair loss is unclear.

Genetic testing may predict female pattern baldness

The HairDX genetic screening test, prior to the onset of symptoms, is used to predict whether a woman will experience pattern hair loss. The test is sold to doctors in a kit, is administered by a simple cheek swab and tests for the gene variant, or CAG repeat.

The test provides women with a CAG Repeat Score. A smaller number in the CAG test score is associated with a higher risk for significant hair loss (Ludwig grade II or III hair loss), while a larger test score is associated with a lower risk for hair loss. "I think the test has probably identified a predictor of female pattern hair loss, but not the only predictor,” says Dr. Schweiger. "There is science behind the test and some published research studies; however, the longitudinal, larger studies have not been done, because this testing procedure is just too new.”

Any genetic testing should be performed under a doctor's supervision so that it can be put in the context of a careful history, a physical examination and a densitometry hair evaluation advises Dr. Schweiger.

Author Bio :

Naomi Mannino is a freelance writer who writes about health, beauty, and fashion. She is a contributing writer for HairLossDotCom and writes about hair loss conditions such as female pattern baldness and male pattern baldness.