Physiologic GH secretion evaluation by means of mean nocturnal GH concentration assessment

Abstract

Standard provocative stimulation tests for GH cannot always determine the actual physiologic secretion of GH. Subjects have been described who respond to pharmacologic tests but show a reduced physiologic secretion as evaluated by means of multiple serum GH measurements over 24 hours and successfully respond to hGH therapy. Reliability of a 12-hr GH spontaneous secretion evaluation was assessed. 27 subjects with short stature due to familial short stature (FSS), constitutional growth delay (CGD), total GH deficiency (TGHD), partial GH deficien cy (PGHD) or with idiopathic short stature (ISS) were studied. Mean nocturnal GH concentration (MNGHC)shows a statistically significant difference between controls (children with FSS) and children with TGHD (P<0.001)with no overlap between the two groups.MNGHC shows intermediate values in children with PGHD. All the patients with ISS, who had a normal response to pharmacologic tests, showed a reduced MNGHC. One of these patients showed a good height velocity increase during hGH therapy. In all subjects a significant correlation (P<0.001) between MNGHC and plasma SMC levels was observed while no correlation resulted between MNGHC and maximal GH response to pharmacologic stimuli. A significant correlation (P<0.001) between MNGHC and height velocity was observed. Our data show the full reliability of physiologic GH secretion assessment over a 12-hour night-time interval.