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Genetic Traits

Male Baldness

Can we categorize the male pattern baldness (MPB), or androgenetic alopecia (AGA) as a disease? Some says yes because there are two FDA approved treatment drugs for this “disease.” Some says no, because there is no physical harm to the person experiencing MPB. Regardless of the final verdict, treatment of MPB is good business with annual sales close to one billion dollar. And the understanding the genetic basis of this common trait is essential for our understanding other common diseases, such as prostate cancer, coronary artery disease and diabetes, all of which might have related to the male pattern baldness.

Follicle is a cavity in the skin where each hair sits in. Over time the follicle can shrink causing the hair to become shorter and finer. Ordinarily, the hair should grow back but in men who are balding the very small follicle ceases to grow any hair.

MPB is easily recognizable. It starts with gradually receding hairline that forms an "M" shape. Eventually the hair becomes finer, shorter, and thinner, and creates a U-shaped (or horseshoe) pattern of hair around the sides of the head. The cause of baldness is not well understood, but is thought to be related to multiple genes and male sex hormones of the individual.

It is suggested that hair follicles of people with early onset of MPB are inheritedly sensitive to dihydrotestosterone (DHT). DHT is a derivative or by-product of testosterone. And DHT is a more powerful androgen than testosterone for its higher affinity to androgen receptor.

Finasteride, one of the two and more effective prescription drugs for MPB, works as an inhibitor for 5-alpha reductase, the enzyme that converts testosterone to DHT. When several mutations in androgen receptor gene were discovered in men with early onset of MPB in 2005, the first solid line of genetic determination of MPB was established. Because androgen receptor gene is located on X-chromosome, one of the sex-chromosome that is passed from mothers to sons, it has been (mis-) interrelated that MPB is inherited from maternal grandfather.

Based on our current understanding, the androgen gene confers only 40% of MPB. Other genes controlling hair follicle cycle, response to metabolic states, cell division, stress and environmental factors confer the other 60%.

In recent years, baldness in men has become more socially acceptable. These phenomena were amplified by famous charismatic bald men, such as Michael Jordan, Bruce Willis, Vin Diesel, Jack Nicholson, Sean Connery, Patrick Stewart, and Ben Kingsley. Therefore claims glorifying baldness have been made, such as "Bald men are more 'virile' or sexually active than others" and “baldness exemplifies higher and frequent intellectual activity." However, unlike skin color, another polygenetic trait, the genetic linkage to beneficial traits unrelated to hair loss has not been proven empirically.

 

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