Steroid 17, 20‐desmolase Deficiency: A New Cause of Male Pseudohermaphroditism

SUMMARY In a child with male pseudohermaphroditism (ambiguous external genitalia, XY sex chromosomal constitution and normal adrenocortical function), incubations of testicular tissue with pregnenolone/progesterone, 17α‐hydroxy‐pregnenolone/17α‐hydroxyprogesterone and androstenedione/dehydroepiandrosterone showed that testosterone could be formed from androstenedione and dehydroepiandrosterone only, but not from other substrates. In urine, testosterone did not increase after HCG, but small amounts of pregnanetriolone were found, which increased after HCG and ACTH. There was no DHA increment after ACTH. It is concluded that this patient, as well as a first cousin and a gonadectomized maternal 'aunt' with the same clinical and urinary steroid findings have testicular and adrenal steroid 17,20‐desmolase deficiency, causing a defect of androgen biosynthesis, which has not previously been described. The heredity of this condition seems to be autosomal or X‐chromosomal.