GENETIC-ANALYSIS OF MALE PATTERN BALDNESS AND THE 5-ALPHA-REDUCTASE GENES

Genetic predisposition and androgen dependence are important character istics of the common patterned loss of scalp hair known as male patter n baldness. The involvement of the 5 alpha-reductase enzyme in male pa ttern baldness has been postulated due to its role in the metabolism o f testosterone to dihydrotestosterone. There are two known isozymes of 5 alpha-reductase. Type I has been predominantly localized to the ski n and scalp. Type II, also present on the scalp, is the target of fina steride, a promising treatment for male pattern baldness. We conducted genetic association studies of the 5 alpha-reductase enzyme genes (SR D5A1 on chromosome 5 and SRD5A2 on chromosome 2) using dimorphic intra genic restriction fragment length polymorphisms. From a population sur vey of 828 healthy families comprising 3000 individuals, we identified 58 young bald men (aged 18-30 y) and 114 older nonbald men (aged 50-7 0 y) for a case control comparison. No significant differences were fo und between cases and controls in allele, genotype, or haplotype frequ encies for restriction fragment length polymorphisms of either gene. T hese findings suggest that the genes encoding the two 5 alpha-reductas e isoenzymes are not associated with male pattern baldness. Finally, n o clear inheritance pattern of male pattern baldness was observed. The relatively strong concordance for baldness between fathers and sons i n this study was not consistent with a simple Mendelian autosomal domi nant inheritance. A polygenic etiology should be considered.