Indirect evidence of chronic Leydig cell desensitization in Klinefelter's syndrome

The basal plasma 17α-hydroxyprogesterone (17-OHP) and testosterone (T) levels were proportionally decreased in 10 hypergonadotropic patients with Klinefelter's syndrome. The ratio 17-OHP to T was however about twice as high as in 10 eugonadal male controls, suggesting the presence of a block in the conversion of 17-hydroxylated steroids to androgens in the Klinefelter patients under basal circumstances. Administration of human chorionic gonadotrophin (hCG, 1500 IU im daily for 3 days) to the Klinefelter patients disclosed a response pattern quite different from that observed in controls. In the control subjects 17-OHP and the ratio 17-OHP/T sharply rose to maximum values at 24 h after the first injection. Thereafter both progressively fell to lowest values at 72 h, when T levels reached their maximum. In the Klinefelter patients the T response to hCG administration was greatly diminished but the 17-OHP response was similar to that in the controls. Maximum 17-OHP and 17-OHP/T values however were not achieved until 72 h after the first injection when T levels also reached their maximum. Unlike in the controls in the Klinefelter patients maximum 17-OHP and T increments and the 17-OHP and T levels 48 and 72 h after the injection were positively correlated. Together the findings of a decreased T synthesis and reserve in the presence of relative 17-OHP accumulation, further increasing after acute hCG administration in a pattern quite different from that in normal men, suggest that in Klinefelter's syndrome the Leydig cells may be chronically desensitized by the persistent endogenous hypergonadotropism.