Hormone profiles and contralateral testicular histology in Down's syndrome with unilateral testicular tumor.

Hormonal profiles and testicular histology were studied in two patients with Down's syndrome with unilateral testicular tumor. Plasma levels of LH and FSH were elevated above normal ranges in both cases. In case 1, plasma testosterone level was abnormally low, but prolactin level in plasma was within the normal range. Case 2 showed elevated concentration of plasma prolactin and normal level of plasma testosterone. The administration of LH-RH resulted in low response of plasma gonadotropins. The response of plasma testosterone to the administration of HCG was abnormally suppressed in both cases. Testicular histology showed reduction of Johnsen score count and tubular diameter, and an increase in wall thickness. These results indicated that male patients with Down's syndrome have an abnormality in hypothalamo-pituitary-gonadal axis.