Role of food intake in the modulation of hexarelin-induced growth hormone release in normal human subjects

Hexarelin (HEX) is a new synthetic analog of the Growth Hormone releasing p eptides and is stronger than GHRH in releasing GH in vivo. No information i s available on the effect of food ingestion on HEX-induced GH secretion. On the other hand, we have previously demonstrated that food intake at luncht ime in normal subjects has an inhibitory effect on the GH response to GHRH. The aim of the present study was to investigate the effect of food ingesti on on GH secretion induced by HEX as compared to GHRH in six normal men (ag ed 23-29 years) and six normal women (aged 24-29 years). The body weights f or all subjects were within 120% of their ideal body weight, according to t heir sex and age. Our data confirm that HEX is much more powerful than GHRH in inducing GH release in humans, both in the fasting state (GH-AUC: 3010 +/- 695 after HEX, vs. 1339 +/- 281 after GHRH, mu g/L/120 min; p < 0.06) a nd after a meal (GH-AUC: 1523 +/- 121, after HEX, vs. 309 +/- 61, after GHR H, mu g/L/120 min; p < 0.06). Moreover, our study shows that food intake pa rtially blunts the fasting GH response to HEX (GH-AUC: 3010 +/- 695 after H EX, in fasting state, vs. 1523 +/- 121 after HEX, after meal, mu g/L/ 120 m in; p<0.06; mean inhibition of AUC 41.02 +/- 7.96%), whereas it nearly abol ishes the GH response to GHRH in the same subjects (GH-AUC: 1339 +/- 281 af ter GHRH, in fasting state, vs. 309 +/- 61 after GHRH, after meal, mu g/L/1 20 min; p<0.06; mean inhibition of AUC 70.31 +/- 6.22%). In conclusion, our study confirms that HEX acts differently from GHRH; the GH releasing effec t of HEX could be only partially influenced by the physiological metabolic or neuroendocrine food-related modifications.