|MadSci Network: Genetics|
Dear John, Thanks for your great question! In general, baldness results from a disturbance in the cycle of normal hair growth and can be temporary or permanent. There are a number of factors which may contribute to temporary hair loss including stress, childbirth, birth control pills, high fever, excessive hair-styling treatments, inadequate protein or iron in the diet, underactive or overactive thyroid, and some cancer treatments. Common baldness (also known by it scientific name, androgenetic alopecia) is the most frequent type of permanent hair loss. It is typically found in males, where it is referred to as "male pattern baldness". However, it can also occur in females. The exact cause of male pattern baldness is not understood, and it is likely that there are many contributing factors. Genetics is certainly one of them. It is thought that hormone levels, such as testosterone, also play a role. Unfortunately, we know very little about the genes that cause male pattern baldness. Though it is a commonly held belief, there is no convincing evidence to suggest that this type of hair loss is inherited from the mother. In fact, although many scientists claim that male pattern baldness is caused by a defect in a single gene, it is likely that it is due to abnormalities in several genes. There are other types of permanent baldness that are inherited and in which the genetics are better understood. Alopecia universalis is a rare, inherited form of baldness that involves hair loss over the entire body. It has been shown recently that this disease is transmitted in an autosomal recessive manner and is due to defects in a gene referred to as the 'hairless' gene. REFERENCES There is an abundance of information on the World Wide Web. However, I should warn you that it is not all entirely accurate or objective. The genetics of male pattern baldness is currently a very confusing area. Most of the information you will find at a particular site only gives one side of the story. However, Online Mendelian Inheritance in Man (OMIM) gives a nice summary of some of the different genetic theories. If you are interested, here is the title of an article given to me by a prominent investigator in the field of baldness research, Dr. Angela M. Christiano. It goes into the theoretical reasons why male pattern baldness is likely due to several genes, rather than just one. It also talks a little about the roots of the "myth" that common baldness is passed on through the mother's side. If you can't find it at your library, please let me know and I will send you a copy. Kuster, W. and Happle, R. Journal of the American Academy of Dermatology. 11:921-926, 1984. I hope you find this information helpful! Please feel free to email me with further questions! Nikki
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