Editorial Note:
Some people have interpreted this story as saying that DHT does not cause baldness. That is not the case. The study only shows that the genes for DHT production are not abnormal, meaning they are not overproducing DHT. This does not change the fact that DHT is linked to hair loss even at normal levels in men who are genetically susceptible to male pattern hair loss.
A recent study in the Journal of Investigative Dermatology studied 828 healthy families comprising 3000 individuals. They studied both young, bald individuals as well as older, non-bald individuals and compared the genes controlling 5-alpha reductase activity (DHT production). It was found that the genes between all the individuals showed no differences. In other words, the genes that control DHT production in men are NOT the cause of male pattern baldness. Some have theorized recently that it could be that the genes for DHT production in balding men caused a higher production of DHT, thus causing baldness. This study shows that there is no overproduction of DHT, or if there is it is not caused by the genes that control DHT production (5-alpha reductase activity).
Another interesting finding of the study was that baldness did not follow a simple genetic inheritance pattern. The study suggests researching the possibility of multiple genes controlling hair loss.
Abstract:
Genetic predisposition and androgen dependence are important characteristics of the common patterned loss of scalp hair known as male pattern baldness. The involvement of the 5alpha-reductase enzyme in male pattern baldness has been postulated due to its role in the metabolism of testosterone to dihydrotestosterone. There are two known isozymes of 5alpha-reductase. Type I has been predominantly localized to the skin and scalp. Type II, also present on the scalp, is the target of Finasteride, a promising treatment for male pattern baldness. We conducted genetic association studies of the 5alpha-reductase enzyme genes (SRD5A1 on chromosome 5 and SRD5A2 on chromosome 2) using dimorphic intragenic restriction fragment length polymorphisms. From a population survey of 828 healthy families comprising 3000 individuals, we identified 58 young bald men (aged 18-30 y) and 114 older non-bald men (aged 50-70 y) for a case control comparison. No significant differences were found between cases and controls in allele, genotype, or haplotype frequencies for restriction fragment length polymorphisms of either gene. These findings suggest that the genes encoding the two 5alpha-reductase isoenzymes are not associated with male pattern baldness. Finally, no clear inheritance pattern of male pattern baldness was observed. The relatively strong concordance for baldness between fathers and sons in this study was not consistent with a simple Mendelian autosomal dominant inheritance. A polygenic etiology should be considered.
Author:
Ellis JA; Stebbing M; Harrap SB
Address:
Department of Physiology, The University of Melbourne, Parkville, Victoria, Australia.
Source:
J Invest Dermatol, 110(6):849-53 1998 Jun
Language:
English
