It is now generally agreed that growth hormone probably plays a physiological role in the regulation of carbohydrate and lipid metabolism. The effects of the hormone, however, are complex and vary greatly with the conditions under which the experiments are performed and, to a lesser extent, with the species studied. Under appropriate circumstances, growth hormone can be shown to increase the concentration of glucose in the blood, while under other circumstances it produces severe hypoglycemia. Sometimes growth hormone increases the uptake of glucose by isolated tissues, and at other times it inhibits glucose uptake. Similarly, growth hormone may either increase or decrease the concentration of free fatty acids (FFA) in the plasma’and may either stimulate or inhibit the synthesis of long-chain fatty acids in adipose tissue.

Certain generalizations can be made to clarify somewhat this state of affairs. Those effects which favor increased utilization of glucose and the storage of fat have been referred to as “insulin-like.” They are the early effects and occur within the first hr after the administration of growth hormone. Hypophysectomy and a high carbohydrate diet4 appear to increase susceptibility to these early effects.