Androgenetic alopecia

Synonyms

1

Overview

Androgenetic alopecia is a common form of hair loss in both men and women. In men, this condition is also known as male-pattern baldness. Hair is lost in a well-defined pattern, beginning above both temples. Over time, the hairline recedes to form a characteristic "M" shape. Hair also thins at the crown (near the top of the head), often progressing to partial or complete baldness.

The pattern of hair loss in women differs from male-pattern baldness. In women, the hair becomes thinner all over the head, and the hairline does not recede. Androgenetic alopecia in women rarely leads to total baldness.

Androgenetic alopecia in men has been associated with several other medical conditions including coronary heart disease and enlargement of the prostate. Additionally, prostate cancer, disorders of insulin resistance (such as diabetes and obesity), and high blood pressure (hypertension) have been related to androgenetic alopecia. In women, this form of hair loss is associated with an increased risk of polycystic ovary syndrome (PCOS). PCOS is characterized by a hormonal imbalance that can lead to irregular menstruation, acne, excess hair elsewhere on the body (hirsutism), and weight gain.

Symptoms

In addition to male-pattern baldness, androgenetic alopecia in men has been associated with several other medical conditions including coronary heart disease and enlargement of the prostate. Additionally, prostate cancer, disorders of insulin resistance (such as diabetes and obesity), and high blood pressure (hypertension) have been related to androgenetic alopecia in men. In women, androgenetic alopecia is associated with an increased risk of polycystic ovary syndrome (PCOS), which is characterized by a hormonal imbalance that can lead to irregular menstruation, acne, excess body hair (hirsutism), and weight gain.

Causes

A variety of genetic and environmental factors likely play a role in causing androgenetic alopecia. Although researchers are studying risk factors that may contribute to this condition, most of these factors remain unknown. Researchers have determined that this form of hair loss is related to hormones called androgens, particularly an androgen called dihydrotestosterone. Androgens are important for normal male sexual development before birth and during puberty. Androgens also have other important functions in both males and females, such as regulating hair growth and sex drive.

Hair growth begins under the skin in structures called follicles. Each strand of hair normally grows for 2 to 6 years, goes into a resting phase for several months, and then falls out. The cycle starts over when the follicle begins growing a new hair. Increased levels of androgens in hair follicles can lead to a shorter cycle of hair growth and the growth of shorter and thinner strands of hair. Additionally, there is a delay in the growth of new hair to replace strands that are shed.

Although researchers suspect that several genes play a role in androgenetic alopecia, variations in only one gene, AR, have been confirmed in scientific studies. The AR gene provides instructions for making a protein called an androgen receptor. Androgen receptors allow the body to respond appropriately to dihydrotestosterone and other androgens. Studies suggest that variations in the AR gene lead to increased activity of androgen receptors in hair follicles. It remains unclear, however, how these genetic changes increase the risk of hair loss in men and women with androgenetic alopecia.

Researchers continue to investigate the connection between androgenetic alopecia and other medical conditions, such as coronary heart disease and prostate cancer in men and polycystic ovary syndrome in women. They believe that some of these disorders may be associated with elevated androgen levels, which may help explain why they tend to occur with androgen-related hair loss. Other hormonal, environmental, and genetic factors that have not been identified also may be involved.

Diagnosis

  • The most important aspects are the history and the physical examination.
  • In the case of a woman, if virilization is evident, laboratory analysis of dehydroepiandrosterone (DHEA)-sulfate and testosterone may need to be obtained. Some authors have suggested that total testosterone level alone may be adequate to screen for a virilizing tumor.
  • If a thyroid disorder is suspected, obtaining a thyrotropin level is indicated.

Treatment

US Food and Drug Administration (FDA)  has approved only 2 drugs in indications for treatment of androgenetic alopecia:

Minoxidil: Appears to lengthen the duration of the anagen phase (the active growth phase of hair follicles), and it may increase the blood supply to the follicle. Regrowth is better at the top of the head than in the front areas and is not noted for at least 4 months. It is used as a 2% or a 5% solution that rubs into the scalp and the 5% solution may work better. However, if the treatment is stopped the baldness returns. It works better in patients who just starting having the alopecia and who have small areas of hair loss.

Finasteride: It can only be used in men and is better for balding at the top of the head. If the treatment is stopped the baldness returns. It cannot be used in women who are still able to have children because it can result in ambiguous genitalia in male babies and it does not seem to be effective in women. The doses are about 1 mg daily by mouth.

Minoxidil use for several months can result in an eye condition known as central chorioretinopathy (an eye disease that lead to temporary visual impairment) , which can go back to normal after 1 months of not using the drug. Finasteride has no known side effects in men, according to several studies, but it cannot be used in women who are still trying to have children because it may produce fetal genital malformations.[1]

Every patient is unique and only the doctor can evaluate and determine the best treatment.

Some drugs that are not approved by the FDA but may be helpful are:

  • Spironalactone: In women with androgenetic alopecia
  • Oral contraceptives: In women
  • Dutasteride: Is currently in study
  • Topical latanoprost 0.1% is currently used to treat glaucoma and using it results in an increase of eyelashes. Some studies have shown that this medication could be useful for stimulating hair follicle activity and treating hair loss
  • Follistatin, a human cell derived medication is also in study

 

Also, low-level laser light therapy, a red light hairbrush–like device has shown some good results.

Surgical treatment of androgenetic alopecia has good cosmetic results. The main problem is covering the bald area with donor plugs (or follicles) sufficient in number to be effective. Micrografting produces a more natural appearance than the old technique of transplanting plugs.

It is important for the patients with androgenetic alopecia to be evaluated for treatable causes of "telogen effluvium" (diffuse hair shedding, often starting suddenly) like anemia or hypothyroidism, especially in patients who had a rapid progress of their disease or a sudden start of the disease. The following treatment options are recommended for women by some experts:

  • Spironolactone and cyproterone acetate
  • Finasteride
  • Minoxidil

These treatments are most effective when started early.

Resources

  • NIH
  • Genetics Home Reference