|MadSci Network: Genetics|
Hmm. I'm kind of short on authoritative references here, but from anecdotal evidence i would say that some people definitely grow hair faster than others. My wife and I recently had a baby, and the mother's hair growth definitely increases during pregnancy, and slows afterward. On the other hand, I have heard that malnutrition can lead to slow hair growth and even hair loss. Hormonal changes definitely increase the growth rate and character of pubic hair, as well as facial hair in males, but I'm not certain whether puberty has any effect on scalp hair. I did have one friend who went from straight to dramatically curly around fifteen, but he's pretty much the exception that proves the rule. I can definitely say that there isn't much you can do to change a given person's hair growth rate. Hair grows in a cycle: during anagen the hair grows, and then in telogen growth ceases and the hair falls out. For example, eyebrow hair follicles have a relatively short anagen period in everyone except my father in law, growing to a normal length of about 10 mm before falling out. Follicles on the scalp normally have a much longer anagen phase, allowing growth to lengths of over a meter. Recent "hair regrowth" drugs such as Rogaine and Propecia prolong anagen, but do not increase the rate of growth of the hair during anagen. So at this time there isn't much that can be done to either increase or decrease the rate of hair growth. As for the influence of genetics on hair growth, I am sure there is an effect but I'm not aware of any efforts to study it in normal individuals. Most hair growth research is currently conducted on androgenetic alopecia, more commonly known as male pattern baldness. As mentioned above, androgenetic alopecia is not a question of the rate of growth of a given hair, but of the rate of the anagen/telogen cycle in each follicle. Finally, I don't really know how the rate of facial hair growth correlates to the rate of scalp hair growth. I am aware of friends who develop five o'clock shadow well before five o'clock, while it takes me two or three days, but I suspect that it is more a matter of hair pigmentation than rate of growth. I'm sorry I can't be more authoritative on your topic. An excellent web reference for the basic biology of hair is: http://www.keratin.com/aa/aaindex.shtml The scientific evidence they cite holds up well against what I already knew of hair biology, so I'd say they're fairly trustworthy. You could also check out propecia.com and rogaine.com, but these sites are definitely more interested in selling you product than educating you. Chris Carlson firstname.lastname@example.org
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