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Growth hormone deficiency is not associated with impaired vagal cholinergic nervous system activity in children
A Hanukoglu1, S Chalew, A A Kowarski
1Department of Pediatrics, University of Maryland School of Medicine, Baltimore 21201.
Insights
Growth hormone (GH) deficiency is not linked to impaired pancreatic polypeptide (PP) response to hypoglycemia in children. However, the PP response magnitude inversely correlates with hypoglycemia severity.
Area of Science:
- Endocrinology
- Neuroendocrinology
- Autonomic Nervous System Function
Background:
- Central cholinergic pathways regulate growth hormone (GH) and pancreatic polypeptide (PP) secretion.
- The relationship between GH deficiency and autonomic responses, specifically PP secretion during hypoglycemia, is not well understood.
Purpose of the Study:
- To investigate if impaired GH secretion is associated with a defective PP response to insulin-induced hypoglycemia in children.
- To explore correlations between PP, epinephrine, and norepinephrine responses during hypoglycemia in pediatric GH deficiency.
Main Methods:
- Studied PP, epinephrine, and norepinephrine responses to insulin-induced hypoglycemia in 31 children with varying GH secretion.
- Categorized patients into controls, subnormal integrated concentration of GH (IC-GH), and GH deficiency groups based on insulin-arginine stimulation test (IATT) and IC-GH.
Main Results:
- Pancreatic polypeptide (PP) levels peaked at glucose nadir and remained elevated, with no significant differences in peak PP or incremental change among groups.
- The peak PP response was inversely correlated with the glucose nadir (r = -0.5, p < 0.005).
- Peak PP levels positively correlated with peak epinephrine levels (r = 0.6, p < 0.001) but not norepinephrine.
Conclusions:
- Growth hormone (GH) deficiency disorders in children are not associated with impaired vagal cholinergic responses to hypoglycemia.
- The magnitude of the PP response in children is inversely related to the degree of hypoglycemia.
- Peripheral hormonal manifestations of autonomic nervous system responses, measured by PP and epinephrine, are closely correlated during hypoglycemia.
Abstract:
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.