GH SECRETION IN PRADER-LABHARD-WILLI SYNDROME - SOMATOTROPE RESPONSIVENESS TO GHRH IS ENHANCED BY ARGININE BUT NOT BY PYRIDOSTIGMINE

Low somatotrope responsiveness to secretagogues has been reported in p atients affected by Prader-Labhard-Willi Syndrome (PLWS). In normal su bjects, GH response to GHRH is known to be greatly potentiated to the same extent by pyridostigmine (PD) or arginine (ARG) which probably ac t via inhibition of hypothalamic somatostatin release. To clarify soma totrope responsiveness in 7 PLWS patients, we studied GH response to G HRH alone and to GHRH combined with PD or ARG. Eight normal short chil dren were studied as controls (NC), GH response to GHRH in PLWS was lo wer than in Ne (AUG: 615 +/- 205 mu g/l-h, vs 1271 +/- 333 mu g/l-h, p < 0.02), In NC, the GHRH-induced GH rise was potentiated to the same extent by PD or ARG. In contrast, in PLWS PD failed to increase the GH response to GHRH (AUG: 615 +/- 205 mu g/l-h vs 621 +/- 176 mu g/l-h, n.s.) which was enhanced by ARG (AUG: 615 +/- 205 mu g/l-h vs 1633 +/- 425 mu g/l-h, p < 0.02), However, the GH response to GHRH + ARG in PL WS was lower than in NC. In conclusion, our results demonstrate that i n PLWS the low somatotrope responsiveness to GHRH is not enhanced by c holinergic potentiation while it is increased by arginine.