5alpha-reductase activity of genital and nongenital skin fibroblasts from patients with 5alpha-reductase deficiency, androgen insensitivity, or unknown forms of male pseudohermaphroditism.

Serially subcultured fibroblast strains from genital (foreskin, labium majus) skin, as a group, have considerably more steroid (testosterone) 5alpha-reductase activity than those form nongenital skin. Foreskin strains varied 40-fold and labial strains even more. Labial strains overlapped nongenital strains of either sex more frequently than did prepuce strains. The activity of foreskin strains from two siblings with proven 5alpha-reductase deficiency was clearly lower than that of any of 18 control stains. The comparative behavior of the various strain types indicates that labial and nongenital strains should not be used to support a clinical suspicion of male pseudohermaphroditism due to 5alpha-reductase deficiency. The activities of labial strains from patients with complete androgen insensitivity (testicular feminization) - five with the receptor-negative variety and two with the receptor-positive type - were as variable as those of control labial strains. The decreased 5alpha-reductase activity observed in fresh skin slices of some patients is probably and expression of their functional estrogen/androgen imbalance in vivo.