Androgen receptor disorder in three brothers with bifid prepenile scrotum and hypospadias.

Three brothers with congenital transposition of the penis, scrotal hypospadias, bifid scrotum, and bilateral undescended testes are described. Further signs of incomplete virilization, but no gynecomastia were seen. LH and FSH were elevated, whereas testosterone levels were reduced or in the normal range. Serum concentrations of 17-hydroxyprogesterone, dehydroepiandrosterone, androstenedione, 5 alpha-dihydrotestosterone and estradiol measured in two affected brothers were in the normal range. Fibroblasts from scrotal skin biopsies performed in two patients showed normal 5 alpha-reductase activity (419 and 214 pmol.(mg protein)-1.h-1; normal greater than 1), whereas androgen receptors had reduced maximal binding capacity (Bmax 4 and 14 fmol.(mg protein)-1; normal greater than 18) and an increased equilibrium dissociation constant (0.7 and 1.26 nmol/l: normal 0.2 +/- 0.08) indicating a quantitative and qualitative androgen receptor defect. These patients represent a further variant of androgen insensitivity.