Low plasma norepinephrine responses to acute hypoglycemia in children with isolated growth hormone deficiency

Norepinephrine (NE) is a neurotransmitter of the sympathetic nervous system which is important in GH secretion. It also is a counterregulatory hormone which is released in response to insulin hypoglycemia. We measured the plasma NE, epinephrine, GH, and cortisol responses to insulin-induced hypoglycemia in 29 short healthy children. The 8 patients (5 males and 3 females) which had isolated GH deficiency had no plasma NE response to insulin hypoglycemia, whereas mean plasma NE increased 2-fold in the 21 GH-sufficient children. Plasma epinephrine concentrations increased in both groups, but were lower in the GH-deficient patients. While these findings do not permit us to determine whether the reduced plasma catecholamine responses to acute hypoglycemia are the cause, the consequence, or unrelated to the GH deficiency, we speculate that there is a relationship between the NE and GH deficiencies.