Failure of dexamethasone and ACTH to suppress plasma testosterone in cryptorchid boys.

Cryptorchid boys show evident alterations in the fine structure of the testes, although they respond in a normal manner to various tests of endocrine function. On the other hand, there is evidence that glucocorticoids suppress plasma testosterone levels, although the mechanism is unknown. Eight control subjects and 8 bilaterally cryptorchid boys, at P1 stage of sexual maturation, were therefore studied by determining the degree of testosterone suppression induced by glucocorticoids. The subjects were submitted to a short dexamethasone (DXM) suppression (1.5 + 0.5 mg at 20.00 and 24.00 h, respectively) and to a short iv ACTH stimulation (1 U/m2 body surface). Basal concentrations of cortisol, androstenedione and testosterone were similar in both groups. Cortisol and androstenedione responded to both DXM suppression and ACTH stimulation in an identical manner in the two groups. DXM lowered the basal levels of testosterone by 46.4 +/- 5.8% (mean +/- SE) in the controls, but only by 6.9 +/- 6.6% in the cryptorchid boys (P less than 0.001). ACTH only induced a significant decrease in the controls (from 110.9 +/- 18.5 to 61.4 +/- 10.9 and 72.3 +/- 11.8 pg/ml (P less than 0.025), after respectively 20 and 30 min), while no significant differences were found in the cryptorchid subjects. These data indicate that in bilateral cryptorchidism, plasma T is not affected by exogenous (DXM) or endogenous (cortisol) glucocorticoids.