Phallic growth after hCG. A clinical index of androgen responsiveness.

Clinical and hormonal responses to a standard three-day human chorionic gonadotropin (hCG)-stimulation test (1,500 IU given intramuscularly for three days) were studied in six neonates with ambiguous genitalia. All patients were eventually determined to be 46,XY genetic males with a microphallus and various other genital abnormalities. None had an enzymatic defect in steroidogenesis or a 5 alpha-reductase deficiency, as determined by standard adrenocorticotropic hormone (ACTH) and hCG testing. All patients demonstrated penile growth (0.25 to 0.75 cm) within five days of hCG administration, with four of six patients achieving a normal penile length (> 2.0 cm) by 48 hours after the last of three daily hCG injections. Androgen responsiveness suggested by phallic growth may help support a male sex assignment in such infants.