Plasma testosterone in Klinefelter's syndrome: diurnal variation and response to ACTH and dexamethasone.

The mean basal plasma testosterone level in 28 patients with chromatin positive Klinefelter's syndrome was significantly lower than in 58 healthy male controls. In 12 of the patients the hormone levels were in the normal range. In both the eugonadal males and the Klinefelter patients the plasma testosterone levels spontaneously decreased throughout the day, the relative decrease in both groups being of the same order of magnitude. Short term ACTH infusion and the administration of dexamethasone did not significantly influence the plasma testosterone concentration in the Klinefelter patients. These findings do not support the view that the adrenal cortex plays a major role in contributing to the circulating plasma testosterone levels in this syndrome.