Androgenic Alopecia (AGA)

The Most Common Cause of Hair Loss?

Hair loss can result from many factors. Some of these include thyroid disorders, high fever, diet, childbirth, and certain medications. The most common form of scalp hair loss is termed androgenetic alopecia ( AGA, or male and female pattern hair loss ). This type of hairloss is NOT caused by poor circulation, clogged hair follicles, frequent shampooing, or the use of hats or helmets.

AGA has 2 common presentation: Receding hairline and thinning crown. AGA is determined by a combination of hereditary factors and male hormones called androgens which include testosterone and dihydrotestosterone (DHT). The tendency for male and female pattern hair loss is genetically inherited from either side of the family and begins to develop after puberty. Hair on the scalp that is genetically affected by DHT (generally the front and top of the scalp), starts to shrink until it is lost. Whereas hair at the back and sides of the scalp is permanent because it is not affected by DHT.

5 Important Points about AGA

•   AGA causes 95% of all hair loss in men, followed by Alopecia Areata (1-2%)
•   AGA progresses with age
•   AGA is unpredictable
•   You may be the first one with AGA in family
•   There is no actual loss of hair follicles

Incidences of AGA in Men

•   19.9% of Chinese have AGA
•   About age 21, 25% of men with AGA first notice hair loss
•   About 25% by age 25-30 will have AGA
•   About 40% by age 40 will have AGA
•   About 50% by age 50 will have AGA

Causes of AGA

Hair loss can result from many factors. Some of these include thyroid disorders, high fever, diet, childbirth, and certain medications. The most common form of scalp hair loss is termed androgenetic alopecia (male and female pattern hair loss). This type of hairloss is not caused by poor circulation, clogged hair follicles, frequent shampooing, or the occasional use of hats or helmets.

AGA is determined by a combination of hereditary factors and male hormones called androgens which include testosterone and dihydrotestosterone (DHT). The tendency for male and female pattern hair loss is genetically inherited from either side of the family and begins to develop after puberty. Hair on the scalp that is genetically affected by DHT (generally the front and top of the scalp), starts to shrink until it is lost. Whereas hair at the back and sides of the scalp is permanent because it is not affected by DHT.

Pathology

The primary pathology is progressive miniaturization of scalp hair transforming to fine vellus hairs. Androgens, specifically dihydrotestosterone (DHT), cause miniaturization in men. Patients with AGA are inherited with hair follicles more sensitive to DHT.

Miniaturization is a complex multifactorial process driven by both genetic and non-genetic factors. Not every follicle is affected at the same time or to the same extent. Miniaturization can take place within a few years for some, or decades for others.

Signs and symptoms

Increase the number of the miniaturized follicles causes baldness. Hair follicles in hairline, midscalp, crown, and temples are most sensitive to DHT. In men the first appearance is therefore a receding hairline and/or thinning crown. Thinning eventually progresses into other areas.

In the more advanced AGA only a rim or "horseshoe" pattern of hair remains. In some men even this remaining rim of hair can be affected by DHT.

Physical Examination

Presence of miniaturized hair follicles smaller than 0.02mm is an early marker of AGA even when a normal number of thick hair is still present. In advance AGA the Terminal/vellus hair ratio change from the normal 8 : 1 to 4 : 1. The total number of hairs remains the same in 90% of cases.

Psychological Impacts of AGA

AGA can adversely affect the social interaction and employment opportunity. Read More

AGA and Coronary Heart Disease

Thinning in the crown, not receding hairline, is associated with risk of heart attack, especially if onset of hair loss before age 30 and with a rapid progression. Frequent check of blood lipid profile is recommended.

•   Mild to moderate AGA: risk increases by 1.3 X
•   Severe AGA: risk increases by 3.4 X

Doctor's Comment

"95% of hair loss in men and 65% in women are from Androgenetic Alopecia. There is no actual hair shedding. The characteristic feature is hair miniaturization in patterned areas."

Dr Damkerng Pathomvanich, MD (USA)