RISE IN PLASMA GROWTH HORMONE IN RESPONSE TO EXOGENOUS LRH IN KLINEFELTER'S SYNDROME

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Abstract
In a group of 16 patients with Klinefelter''s syndrome (KS) aged from 2 yr 8 mo. to 31 yr, the plasma growth hormone (hGH) response to LRH (50 .mu.g/m2 i.v.; n = 16), TRH (200 .mu.g i.v.; n = 14) and insulin-induced hypoglycemia (0.1 U regular insulin/kg i.v.; n = 6) was studied. There was a rise in hGH following LRH from a level below 5 ng/ml during fasting to a level above 8 ng/ml (P < 0.001) in 9 (56.3%) of the 16 patients tested; a similar response was found in only 1 of a control group of 15 boys matched for age. TRH stimulation led to a rise in hGH in 1 of the 14 KS patients tested, with none in the control group. Insulin-induced hypoglycemia elicited a normal response of hGH in the 6 KS patients tested, from 1.8 .+-. 0.7 to 16.5 .+-. 3.7 ng/ml, (mean .+-. SD, P < 0.001). Basal prolactin (PRL) levels were normal in the KS patients (9.4 .+-. 4.1 ng/ml, mean .+-. SD) but the response to TRH stimulation was significantly higher (63.3 .+-. 40 ng/ml; P < 0.01) than that of the control group (30 .+-. 15 ng/ml). Plamsa gonadotropin levels and the response to LRH stimulation were increased in all of the KS patients except those below the age of 13. Plasma TSH levels and the response to TRH stimulation as well as the levels of serum thyroxin were normal in all the KS patients tested. The abnormal rise of hGH following LRH stimulation and of PRL following TRH stimulation suggests a disturbance in the neuroendocrine regulation mechanism of these hormones in KS.