Common baldness in women, also called female pattern alopecia, is genetically inherited and can come from either the mothers or fathers side of the family. Female alopecia most commonly presents in a diffuse pattern, where hair loss occurs over the entire scalp. Less commonly, women exhibit a patterned distribution where most of the thinning occurs on the front and top of the scalp with relative sparing of the back and sides.

The type of hair loss, diffuse or patterned, has important implications for treatment. Women with diffuse hair loss are generally best treated medically, whereas women with patterned hair loss may be good candidates for hair transplant surgery. Interestingly, patterned hair loss is the most common type seen in men and accounts for why a greater proportion of men are candidates for surgery compared to women.

In women who are genetically predisposed to hair loss, both diffuse and patterned distributions are caused by the actions of two enzymes: aromatase (which is found predominantly in women) and 5-a reductase (which is found in both women and men). Diffuse hair loss is most often hereditary, but it can also be caused by underlying medical conditions, medications, and other factors; therefore, a thorough medical evaluation is an important part of the management.

In the next sections, we will take a closer look at both the mechanisms of genetically induced female hair loss as well as the medical conditions and drugs that can cause diffuse hair loss in women.

As with hair loss in men, female genetic hair loss largely stems from a complex stew of genes, hormones, and age. However, in women, there are even more players. In addition to 5-a reductase, testosterone, and dihydrotestosterone (DHT); which are also found in mens hair loss; also present in women are the enzyme aromatase and the female hormones estrone and estradiol. So lets break down the process that leads to common hair loss in women.

In both men and women, 5-a reductase reacts with testosterone to produce DHT, the hormone responsible for the miniaturization (shrinking) and the gradual disappearance of affected hair follicles. This explains why both men and women lose their hair. But one of the reasons why women seldom have the conspicuous bald areas that men do is because women naturally have only half the amount of 5-a reductase compared to men.

Adding to this complexity, in women, the enzyme aromatase is responsible for the formation of the female hormones, estrone, and estradiol, counteract the action of DHT. Women have higher levels of aromatase than men, especially at the frontal hairline. It is this presence of aromatase which may help explain why hair loss in women looks 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 (Propecia), a medication widely used to treat hair loss in men that works by blocking the formation of DHT.

The following is a schematic chart of how the female hormones estrone and estradiol are produced and their relationship to DHT:

Womens hair seems to be particularly sensitive to underlying medical conditions. Since systemic medical conditions often cause a diffuse type of hair loss pattern that can be confused with genetic balding, it is important that women with undiagnosed alopecia be properly evaluated by a doctor specializing in hair loss (i.e., a dermatologist).

Below is a list of medical conditions that can lead to a diffuse pattern of hair loss:

A relatively large number of drugs can cause telogen effluvium, a condition where hair is shifted into a resting stage and then several months later shed. Fortunately, this shedding is reversible if the medication is stopped, but the reaction can be confused with genetic female hair loss if not properly diagnosed. Chemotherapy and radiotherapy can cause a diffuse type of hair loss called anagen effluvium that can be very extensive. This hair loss is also reversible when the therapy is over, but the hair does not always return to its pre-treatment thickness.

Causes of Telogen Effluvium

Causes of Anagen Effluvium

A host of dermatologic conditions can cause localized hair loss in women. The pattern that they produce is usually quite different from the diffuse pattern of female genetic hair loss and is easily differentiated from it by an experienced dermatologist. Occasionally, the diagnosis is difficult to make and tests, such as a scalp biopsy are necessary.

Localized hair loss in women may be sub-divided into scarring and non-scarring types.

Non-Scarring Alopecias

Alopecia Areata is a genetic, auto-immune disease that typifies the non-scarring type. It manifests with the sudden onset of discrete, round patches of hair loss associated with normal underlying skin. It usually responds quite well to local injections of corticosteroids.

Localized hair loss can be also be caused by constant pulling on scalp hair, either through braiding, tight clips or hair systems. Traction alopecia, the medical term for this condition, often causes reversible thinning but, if the tugging on the follicles persists for an extended period of time, the hair loss can be permanent. The most common presentation is thinning, or complete hair loss, at the frontal hairline and in the temples of women who wear their hair pulled tightly back. Early traction alopecia can reverse itself by simply wearing the hair loose. A hair transplant may be needed to restore the hair that is permanently lost from sustained traction.

Scarring Alopecias

Scarring hair loss can be caused by a variety of medical or dermatologic conditions such as Discoid Lupus, Lichen Planus, and infections. It can also be caused by thermal burns or local radiation therapy. Face-lift surgery may result in permanent localized hair loss that can be particularly bothersome if it occurs at the frontal hairline or around the temples. Fortunately, localized hair loss from injury or from medical problems are often amenable to hair transplantation.

Many of the factors that cause the rate of loss to speed up or slow down are unknown, but we do know that with age, a persons total hair volume will decrease. This is referred to as senile alopecia. Even when there is no predisposition to genetic balding, hair across the entire scalp will thin over time resulting in the appearance of less density. The age at which these effects finally manifest themselves varies from one individual to another and is mainly related to a persons genetic makeup.

See the article here:
Causes of Hair Loss in Women | Bernstein Medical

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