STIMULATED GH SECRETION AFTER GHRH PRETREATMENT IN OBESE CHILDREN: EVIDENCE FOR SOMATOSTATIN INCREASE?

The impairment of GH secretion present in obesity could be due to an increase of the somatostatinergic tone or to a reduced pituitary production rate. To further study this problem, we evaluated 27 peripubertal obese children (18 M, 9 F; mean age 10.9±2.5 yrs) in which we studied the GH response to GHRH (n=6), insulin hypoglicemia (n=6), clonidine (n=7) and arginine (n=8) after GHRH pretreatment (1 ug/kg 120 min before the tests) and we compared the results obtained with those of 26 short normal children matched for age and pubertal status. The main results can be summarized as follows: 1) no difference was present in baseline IgfI levels in the two groups. 2) GHRH pretreatment and all the follwing stimuli are able to elicit a significant GH response in obese as in controls, with the exception of arginine which in the latter group did not induce a significant GH increase. 3) No difference was found among the GH response to the second stimuli in obese children, while in controls peak values after arginine were lower than after GHRH and clonidine. 4) The comparison between normal and obese children showed similar baseline values but higher GH levels in controls after all stimuli, but arginine after which no difference was present between the 2 groups. We conclude that the pattern of GH neuroendocrine control is similar in normal and obese children; the different behavious after arginine, which is supposed to act through somatostatin inhibition, might be due to a chronic increase in somatostatinergic tone responsible for the lower stimulated GH levels in obesity.