Evidence for secondary 5 alpha-reductase deficiency in genital and supra-pubic skin of subjects with androgen insensitivity syndrome.

The activity of 5 alpha-reductase in genital and supra-pubic skin (homogenate or fibroblasts) from subjects with complete or incomplete androgen insensitivity syndrome was low compared with mean activity in samples from normally differentiated male controls. Also, in two subjects with incomplete androgen insensitivity syndrome the ratio of the concentration of testosterone to that of 5 alpha-dihydrotestosterone in plasma was raised after hCG stimulation but normal under basal conditions. In three subjects with complete androgen insensitivity syndrome there was no evidence of raised ratios of testosterone to 5 alpha-dihydrotestosterone in plasma under basal or hCG-stimulated conditions. The activities of other steroid metabolizing enzymes, e.g. 17 beta-hydroxysteroid dehydrogenase, 3 alpha/beta-hydroxysteroid dehydrogenase, were not decreased. The low 5 alpha-reductase activity of androgen insensitive subjects reported here, and by others, may imply that this enzyme in genital skin is in some way androgen dependent, or responsive to other factors associated with androgen insensitivity syndrome.