Effect of growth hormone on oral glucose tolerance and circulating metabolic fuels in man

We infused growth hormone into normal subjects in doses that raised circulating hormone to levels (30-35 ng/ml) similar to those seen during stress. Growth hormone excess failed to alter fasting glucose and somatomedin concentrations. However, non-esterified fatty acids and ketones increased by 50% (p less than 0.05) and 120% (p less than 0.01), respectively, despite 35% higher plasma insulin concentrations. When oral glucose was ingested 5 h after initiating the growth hormone infusion, plasma glucose rose by 2-2.5 mmol/l above control (saline infusion) values and the area under the glucose curve increased twofold (p less than 0.005). This occurred in the face of twofold higher insulin levels and normal suppression of glucagon. Growth hormone also did not affect the hyperglycaemic response to a combined infusion of cortisol, glucagon and adrenaline, but accentuated the rise in non-esterified fatty acids, ketones, and insulin caused by these hormones. Our data suggest that growth hormone excess rapidly produces insulin antagonistic effects that may contribute to stress-induced glucose intolerance and lipolysis, even though fasting glucose levels remain unchanged.