The Effect of Free Fatty Acids on Growth Hormone(GH)-Releasing Hormone-Mediated GH Secretion in Man*

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Abstract
The effect of FFA [free fatty-acid] on GH [growth hormone] (GHRH)-mediated secretion of GH was examined in 6 normal young men. Three of the men were infused with 250 ml of a lipid-heparin solution at 1.67 ml/min for 150 min, and the other 3 were given an equivalent volume of saline in the same manner. After the start of infusion (30 min) 100 .mu.g GHRH (the 44-amino acid form) were injected i.v. and plasma GH and FFA were measured. The same men participated in an identical experiment 1 wk later, but the ones who had received lipid-heparin previously were given saline and vice versa. Plasma FFA increased to 2.25 .+-. 0.16 meq/l (mean .+-. SEM [standard error of the mean]) 60 min after the start of lipid-heparin infusion, whereas FFA levels did not change significantly in the saline-treated group. Mean plasma GH levels reached peak concentrations in both groups 30 min after GHRH treatment. The peak GH response when lipid-heparin was given was significantly diminished (8.4 .+-. 1.7 ng/ml), compared with the peak response when saline was given (28.9 .+-. 7.1 ng/ml). Apparently plasma FFA elevations induced by lipid-heparin infusion inhibit GH secretion induced by GHRH.