Effect of Feedingvs. Fasting on Metabolic Changes Produced by Human Growth Hormone in Man1

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Abstract
Repeated determinations were made of venous blood levels of fat and carbohydrate intermediary metabolites in 10 normal subjects fasted for 42 hours, given multiple 2-hr feedings of carbohydrate and fat, and following a single im injection of human growth hormone during fasting and during feeding. Fasting produced no significant changes in the levels of blood glucose and lactate; blood pyruvate, citrate, free fatty acids and ketones increased. Blood urea nitrogen decreased initially but subsequently rose above the control. Feeding produced no significant change in 2-hr postprandial levels of carbohydrate and fat metabolites; blood urea nitrogen steadily decreased. Human growth hormone administered during fasting produced a greater rise in free fatty acids and ketones than that observed during fasting alone, and inhibited the late rise in blood urea nitrogen. Human growth hormone markedly altered the response to multiple feedings by producing a marked rise in 2-hr postprandial levels of glucose, pyruvate, citrate and free fatty acids, and a more pronounced fall in blood urea nitrogen. The immediate metabolic response to growth hormone was more evident in the fed than in the fasted state. In the fed state, growth hormone reproduced the metabolic pattern of fasting and also raised glucose and markedly lowered blood urea nitrogen. The relation of these changes in blood to known metabolic pathways is discussed.