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Androgenetic Alopecia

Androgenetic Alopecia
Last Updated: March 8, 2006 Rate this Article

Synonyms and related keywords: common baldness, familial baldness, hereditary baldness, male pattern baldness, female pattern baldness, pattern baldness, hair loss, androgenic alopecia
Author: Robert P Feinstein, MD, Associate Clinical Professor, Department of Dermatology, Columbia University College of Physicians and Surgeons
Robert P Feinstein, MD, is a member of the following medical societies: American Academy of Dermatology, American Medical Association, Noah Worcester Dermatological Society, and Phi Beta Kappa

Editor(s): Leonard Sperling, MD, Chair, Professor, Department of Dermatology, Uniformed Services University of the Health Sciences; David F Butler, MD, Professor, Texas A&M University College of Medicine; Director, Division of Dermatology, Scott and White Clinic; Edward F Chan, MD, Clinical Assistant Professor, Department of Dermatology, University of Pennsylvania School of Medicine; Catherine Quirk, MD, Clinical Assistant Professor, Department of Dermatology, Brown University; and Dirk M Elston, MD, Director, Department of Dermatology, Geisinger Medical Center


INTRODUCTION Section 2 of 9

Author Information Introduction Clinical Differentials Workup Treatment Medication Follow-up Bibliography

Background: Androgenetic alopecia is an extremely common disorder affecting both men and women. The incidence is generally considered to be greater in males than females, although some evidence suggests that the apparent differences in incidence may be a reflection of different expression in males and females.
Pathophysiology: This genetically determined disorder is progressive through the gradual conversion of terminal hairs into indeterminate hairs and finally to vellus hairs. Patients have a reduction in the terminal-to-vellus hair ratio, normally at least 2:1. Following miniaturization of the follicles, fibrous tracts remain. Patients with this disorder usually have a typical distribution of hair loss.
• Internationally: This is an extremely common disorder that affects roughly 50% of men and perhaps as many women older than 40 years. As many as 13% of premenopausal women reportedly have some evidence of androgenetic alopecia. However, the incidence increases greatly in women following menopause, and, according to one author, it may affect 75% of women older than 65 years.
Mortality/Morbidity: This is essentially a cosmetic disorder. Other than affecting the patient psychologically, the disorder is significant only in that it allows ultraviolet light to reach the scalp and, thus, increases the amount of actinic damage. Males with androgenetic alopecia may have an increased incidence of myocardial infarction. An increase in benign prostatic hypertrophy has also been associated. If these associations are proven conclusively, this disorder will be of greater clinical significance.
Race: The incidence and the severity of androgenetic alopecia tend to be highest in white men, second highest in Asians and African Americans, and lowest in Native Americans and Eskimos.
Age: Almost all patients have an onset prior to age 40 years, although many of the patients (both male and female) show evidence of the disorder by age 30 years.

CLINICAL Section 3 of 9

Author Information Introduction Clinical Differentials Workup Treatment Medication Follow-up Bibliography

• The onset is gradual.
• Men present with gradual thinning in the temporal areas, producing a reshaping of the anterior part of the hairline. For the most part, the evolution of baldness progresses according to the Norwood/Hamilton classification of frontal and vertex thinning.
• Women usually present with diffuse thinning on the crown. Bitemporal recession does occur in women but usually to a lesser degree than in men. In general, women maintain a frontal hairline.
• In both males and females with androgenetic alopecia, the transition from large, thick, pigmented terminal hairs to thinner, shorter, indeterminate hairs and finally to short, wispy, nonpigmented vellus hairs in the involved areas is gradual. As the disorder progresses, the anagen phase shortens with the telogen phase remaining constant. As a result, more hairs are in the telogen phase, and the patient may notice an increase in hair shedding. The end result can be an area of total denudation. This area varies from patient to patient and is usually most marked at the vertex.
• Women with androgenetic alopecia generally lose hair diffusely over the crown. This produces a gradual thinning of the hair rather than an area of marked baldness. The part is widest anteriorly.
• The frontal hairline is often preserved in women with this disorder, whereas men note a gradual recession of the frontal hairline early in the process.
Causes: Androgenetic alopecia is a genetically determined condition. Androgen is necessary for progression of the disorder, as it is not found in males castrated prior to puberty. The progression of the disorder is stopped if postpubertal males are castrated. Androgenetic alopecia is postulated to be a dominantly inherited disorder with variable penetrance and expression. However, it may be of polygenic inheritance. Recently, it was noted that follicles from balding areas of persons with androgenetic alopecia are able to produce terminal hairs when implanted into immunodeficient mice. This suggests that systemic or external factors may play a role in this disorder.
DIFFERENTIALS Section 4 of 9

Author Information Introduction Clinical Differentials Workup Treatment Medication Follow-up Bibliography

Alopecia Areata
Anagen Effluvium
Telogen Effluvium

Other Problems to be Considered:
Alopecia of senescence
Alopecia associated with virilizing disorders of women where it may be seen with hirsutism and menstrual problems
Anagen effluvium after exposure to toxic chemicals, including chemotherapeutic agents
Alopecia associated with hypothyroidism or hyperthyroidism
Telogen effluvium may accelerate androgenetic alopecia, and causes, such as iron deficiency and papulosquamous diseases of the scalp, must be considered. Quick Find
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Alopecia Areata

Anagen Effluvium

Telogen Effluvium

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WORKUP Section 5 of 9

Author Information Introduction Clinical Differentials Workup Treatment Medication Follow-up Bibliography

Lab Studies:
• The most important aspects are the history and the physical examination.
o 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.
o If a thyroid disorder is suspected, obtaining a thyrotropin level is indicated.
• If telogen effluvium is present, laboratory analysis of serum iron levels or a biopsy to note an underlying papulosquamous disorder may be indicated. Telogen effluvium may accelerate the course of pattern alopecia. Iron deficiency is a common and reversible cause of telogen effluvium. A normal CBC count does not exclude iron deficiency as a cause of hair loss. While a low ferritin level is always a sign of iron deficiency, ferritin behaves as an acute phase reactant, and levels may be normal despite iron deficiency. Iron, total iron-binding capacity, and transferrin saturation are inexpensive and sensitive tests for iron deficiency.
• Diffuse alopecia areata may mimic pattern alopecia. The presence of exclamation point hairs, pitted nails, or a history of periodic regrowth or tapered fractures noted on hair counts suggests the diagnosis of diffuse alopecia areata.
• A biopsy is rarely necessary to make the diagnosis. If a single biopsy specimen is obtained, it should generally be sectioned transversely if pattern alopecia is suspected. Some dermatopathologists recommend that if a biopsy is to be performed, a sample should be obtained from 2 sites: one for horizontal sectioning and one for vertical sectioning of the hair follicles. Other dermatopathologists point out that one may commonly obtain sufficient information from serial vertical sections to diagnose the condition.
Histologic Findings: In pattern alopecia, hairs are miniaturized. In evolving-pattern alopecia, the diameter of hair shafts varies. Fibrous tract remnants (so-called streamers) can be found below miniaturized follicles. Although androgenetic alopecia is considered a noninflammatory form of hair loss, at times, a superficial, perifollicular, inflammatory infiltrate is noted. A mildly increased telogen-to-anagen ratio is often observed.
TREATMENT Section 6 of 9

Author Information Introduction Clinical Differentials Workup Treatment Medication Follow-up Bibliography

Medical Care: Only 2 proven, food and drug administration (FDA)-approved medications are currently available for treatment of androgenetic alopecia: minoxidil and finasteride.
• Minoxidil
o Although the method of action is essentially unknown, minoxidil appears to lengthen the duration of the anagen phase, and it may increase the blood supply to the follicle. Regrowth is more pronounced at the vertex than in the frontal areas and is not noted for at least 4 months. Continuing topical treatment with the drug is necessary indefinitely because discontinuation of treatment produces a rapid reversion to the pretreatment balding pattern.
o Patients who respond best to this drug are those who have a recent onset of androgenetic alopecia and small areas of hair loss. The drug is marketed as a 2% or a 5% solution, with the 5% solution being somewhat more effective. A recent 48-week study compared the 2 strengths in men. Findings indicated that 45% more regrowth occurred with the 5% compared with the 2% solution. In general, women respond better to topical minoxidil than men. The increase in effectiveness of the 5% solution was not evident for women in the FDA-controlled studies. Subsequent studies have shown at best a modest advantage to the higher concentration in women. In addition, the occurrence of facial hair growth appears to be increased with the use of the higher-concentration formulation.
• Finasteride
o Finasteride is given orally and is a 5 alpha-reductase type 2 inhibitor. It is not an antiandrogen. The drug can be used only in men because it can produce ambiguous genitalia in a developing male fetus. Finasteride has been shown to diminish the progression of androgenetic alopecia in males who are treated, and, in many patients, it has stimulated new regrowth.
o Although it affects vertex balding more than frontal hair loss, the medication has been shown to increase regrowth in the frontal area as well. Finasteride must be continued indefinitely because discontinuation results in gradual progression of the disorder. A study in postmenopausal women indicated no beneficial effect of the medication in treating female androgenetic alopecia.
• Some drugs are non-FDA-approved but potentially helpful medications. In women with androgenetic alopecia, especially those with a component of hyperandrogenism, drugs that act as androgen suppressants or antagonists (eg, spironolactone, oral contraceptives) may be beneficial.
• Androgenetic alopecia is very common; therefore, not surprisingly, it may accompany other forms of hair loss. Cases of telogen effluvium often occur in patients with underlying androgenetic alopecia. Therefore, a search for treatable causes of telogen effluvium (eg, anemia, hypothyroidism), especially in patients with an abrupt onset or a rapid progression of their disease, is indicated.
Surgical Care:
• Surgical treatment of androgenetic alopecia has been successfully performed for the past 4 decades. Although the cosmetic results are often satisfactory, 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. Patients with less than 40 follicular units/cm2 in their donor areas are poor candidates for the procedure. Scalp reduction has been attempted to decrease the size of the scalp to be covered by transplanted hair. However, the scars produced by the reduction technique often spread and become more noticeable with time.
• Hair weaving techniques are available, and, together with hairpieces, they offer the patient a prosthetic method of coverage.

Escrito por Antonio Rondon Lugo el 29 de junio de 2007 con 0 comentarios.
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