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

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Abstract
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. 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 2000 and 2400 h, respectively) and to a short i.v. 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 2 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 < 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 < 0.025), after, respectively, 20 and 30 min), while no significant differences were found in the cryptorchid subjects. In bilateral cryptorchidism, plasma T apparently is not affected by exogenous (DXM) or endogenous (cortisol) glucocorticoids.