Androgenetic alopecia (common baldness)

Hair loss is universal and inevitable among all humans. Although the process is virtually the physiologic norm, hair has such a powerful role in a person's psychosexual self-image that anxiety about its loss may prompt him or her to seek medical attention. Androgenetic alopecia (AGA) is the most common cuase of hair thinning and occurs in both sexes when there is progressive miniaturization of hair follicles, shortening of the anagen phase of the hair cycle, and prolongation of the telogen phase. The scalp has a 3-phase cycle of hair with almost 90% of hair in the anagen or growth phase (which may last up to 2-6 years), 1% in the catagen phase (which may last 3 weeks), and 10% in the telogen or resting phase (which may last 3 months). This ratio is usually uniformly distributed over the entire scalp.

The impact of hair loss on self-esteem is quite different. Some tolerate it without any concern, while others find it to be unacceptable when hair loss goes beyond culturally defined limits. This is due to this great psychosocial impact, that many patients may seek inappropriate and unproven therapies that are available in nonmedical settings, often at great expense to the consumer.

There is no question that genetic factors have a role in the development of androgenetic alopecia, but the exact mechanism is not known. Inheritance in this condition is most likely polygenic. There is increased frequency of AGA in sons of men with AGA. The maternal influence on AGA is less well defined and the family histories of women with AGA are not as straightforward as those of men with AGA.

There is a myth about role of blood flow in AGA.  This myth has been used to sell hair loss products as bizarre as a device that allows you hang upside down in your closet overnight in order to restore blood flow, but the fact is that blood supply is excellent in the scalp and there is no need to enhance it!

In brief, in AGA, hair loss occurs due to the action of circulating androgens in genetically susceptible men and women. Although testosterone is the major circulating androgen in men, its metabolite, dihydrotestosterone (DHT) is the main culprit in AGA. The conversion of testosterone to DHT is mediated by an enzyme called 5-alpha-reductase. Most women with AGA show no other clinical or biochemical evidence of androgen excess.

Thinning of the hair begins between 12 and 40 years of age in both sexes, and approximately 50% of the population expresses this trait to some degree before 50 years of age. Balding tends to begin earlier in men and to develop in well-recognized patterns while female androgenetic alopecia is more diffuse and less patterned than the forms seen in men.


Before treatment is recommended, patients should be carefully examined to establish the diagnosis and rule out other causes of hair loss by history and physical findings, as well as laboratory tests if needed.

The diagnosis of AGA is usually made from the history and clinical findings alone. Pull test may be positive in active early hair loss, but in the majority miniaturization and decreased hair density are the only signs of AGA. Scalp is also generally normal, however concomitant seborrheic dermatitis is common.

In women, extensive hormonal evaluation may not be needed if the patient has no menstrual irregularities, infertility, hirsutism, severe cystic acne, virilization, or galactorrhea. If one or more of the above symptoms are present in a woman, it may be useful to evaluate the hormonal status. However, in most cases of female AGA, as in almost all cases of male AGA, there are no alterations in the production of hormones and the problem lies in the target organ, that is, how each hair follicle responds to circulating androgens.

Less obvious causes of hair loss, particularly in women, include thyroid disease and other endocrine disorders, poor nutritional status, iron deficiency, drugs, severe infection, systemic disease, malignancy, as well as other causes of telogen effluvium. In addition to telogen effluvium, some variants of alopecia areata and early cicatricial alopecia should also be kept in mind in differential diagnosis of AGA.


A. General principles

B. Medical treatments

1. Topical minoxidil solution: Topical application of minoxidil offers unlimited hope but little practical benefit. It must be used for 4 to 6 months before any results are seen, and new hair growth is generally poor. When therapy is discontinued, the new growth soon falls out, and patients return to their pretreatment condition. Mechanisms include increasing the rate of mitosis of the follicle cells and prolonging the duration of the anagen phase.

         Minoxidil should be applied 1 mL twice daily on dry scalp and requires about one hour to be absorbed.

         Hair growth in areas other than that to which it has been applied is a well-known phenomenon and may make more concern in women.

         Topical minoxidil may also initially cause a temporary shedding which is self-limiting and should not be a cause for concern.

         If minoxidil is discontinued, any positive effect on hair growth will be lost in 4-6 months.

         FDA approved minoxidil for men > 18 years old.

Another topical drug that has shown results is 17 alpha-estradiol applied to the scalp once a day. It was suggested that its action occurs from an aromatase stimulus, with diversion of testosterone metabolism toward the production of 17 beta-estradiol, leading to the reduction of dihydrotestosterone synthesis.

2. In certain selected cases, the following treatments may be helpful in women only: oral estrogen, spironolactone, cyproterone acetate.

3. Oral finasteride (5a -reductase type 2 inhibitor): One milligram (1 mg) of finasteride, a competitive inhibitor of 5-alpha-reductase type 2, taken orally, improves predominantly vertex male pattern hair loss, and it is generally well tolerated. Finasteride produces some regrowth of hair in about 2/3 of men. It is contraindicated for women who are or may become pregnant, as it may cause abnormalities to the external genitalia of the male fetus. FDA approved finasteride only for men > 18 years old.

Safety of finasteride:

C. Surgical therapy

Surgical hair restoration, consisting of the implant of mini- and micro-grafts (transplanting of single hairs or groups of 3 to 6 hairs in the occipital area), provides satisfactory results, and is indicated in the most extensive cases of AGA.

D. Gene therapy

Genetic therapy will probably be available in the next 10 to 20 years as an efficient treatment for AGA.