Growth hormone deficiency is not associated with impaired vagal cholinergic nervous system activity in children.

Central cholinergic mechanisms mediate release of growth hormone (GH) as well as peripheral secretion of pancreatic polypeptide (PP). To determine if impaired ability to secrete GH is associated with defective PP response, we studied the PP, epinephrine, and norepinephrine responses to insulin-induced hypoglycemia in 31 children evaluated for GH deficiency by insulin-arginine stimulation (IATT) and 24-h integrated concentrations of GH (IC-GH). Eleven patients had normal GH by IATT and IC-GH (controls), 10 patients had normal GH by IATT but subnormal IC-GH, 10 patients had GH deficiency by both IATT and IC-GH. PP levels peaked at the time of glucose nadir, and remained elevated for 20 min thereafter. The peak PP and incremental PP change from baseline were not significantly different among the three groups. The log peak PP response was inversely correlated with the glucose nadir (r = -0.5, p less than 0.005). Peak PP levels were also significantly correlated with the peak epinephrine levels (r = 0.6, p less than 0.001) but not with norepinephrine. Our findings suggest that 1) GH deficiency disorders are not associated with impaired vagal cholinergic response to hypoglycemia; 2) in children the magnitude of PP response is inversely related to the degree of hypoglycemia; and 3) the peripheral hormonal manifestation of autonomic nervous system responses to hypoglycemia as measured by PP and epinephrine levels are closely correlated.