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 gradual disappearance of affected hair follicles. This explains why both men and women lose their hair. 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.

Women’s 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).

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.

Common baldness in women, also called female pattern alopecia, is genetically inherited and can come from either the mother’s or father’s 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.

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.
Mechanism of Genetic Hair Loss in Women

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 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.

As with hair loss in men, female genetic hair loss largely stems from a complex stew of genes, hormones and age. In addition to 5-a reductase, testosterone, and dihydrotestosterone (DHT); which are also found in men’s hair loss; also present in women are the enzyme aromatase and the female hormones estrone and estradiol.

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

Causes of Telogen Effluvium.

Localized Hair Loss.

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.

Obstetric and gynecologic conditions; such as post-partum and post-menopausal states or ovarian tumors
Anemia (iron deficiency).
Thyroid disease.
Connective tissue diseases, such as Lupus.
Nutritional causes including crash diets, bulimia, protein/calorie deficiency, essential fatty acid or zinc deficiency, malabsorbtion, and hypervitaminosis A.
Stress from surgical procedures, general anesthesia, or severe emotional problems.

Non-Scarring Alopecias.

Blood thinners (anti-coagulants) such as warfarin and heparin.
Seizure medication (most commonly dilantin).
Medication for gout, colchicines, and alopurinol (Xyloprim).
Blood pressure medication, particularly the b-blockers (such as Inderal) or diuretics.
Anti-inflammatory drugs (such as prednisone).
Medications that lower cholesterol and other lipids.
Mood altering drugs such as lithium, tri-cyclics, Elavil, Prozac.
Thyroid medications.
Oral contraceptive agents, particularly those high in progestins.
Miscellaneous medications, such as diet pills, high doses of Vitamin A, street drugs (cocaine).

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

Localized hair loss can be also be caused by constant pulling on scalp hair, either through braiding, tight clips or hair systems. 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.

Scarring hair loss can be caused by a variety of medical or dermatologic conditions such as Discoid Lupus, Lichen Planus, and infections. Localized hair loss from injury or from medical problems are often amenable to hair transplantation.
Hair Loss in Women & Aging.

Chemotherapy.
Radiotherapy.

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 cortico-steroids.

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 person’s total hair volume will decrease. 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.

Causes of Anagen Effluvium.

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.

Scarring Alopecias.

Drugs That Can Cause Diffuse Hair Loss in Women.

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