Rise in plasma growth hormone in response to exogenous LRH in Klinefelter's syndrome

In a group of sixteen patients with Klinefelter's syndrome (KS) aged from 2 years 8 months to 31 years, a study was made of the plasma growth hormone (hGH) response to LRH (50 micrograms/m2 i.v.; n=16), TRH (200 micrograms i.v.; n=14) and insulin-induced hypoglycaemia (0.1 u R.I,/kg i.v.; n=6). 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 less than 0.001) in nine (56.3%) of the sixteen patients tested; a similar response was found in only one of a control group of fifteen boys matched for age. TRH stimulation led to a rise in hGH in one of the fourteen KS patients tested, with none in the control group. Insulin-induced hypoglycaemia elicited a normal response of hGH in the six KS patients tested, from 1.8 +/- 0.7 to 16.5 +/- 3.7 ng/ml, (M +/- SD, P less than 0.001). Basal prolactin (PRL) levels were normal in the KS patients (9.4 +/- 4.1 ng/ml, M +/- SD) but the response to TRH stimulation was significantly higher (63.3 +/- 40 ng/ml; P less than 0.01) than that of the control group (30 +/- 15 ng/ml). Plasma gonadotrophin 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 thyroxine were found to be 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 mechanisms of these hormones in KS.