LOW SERUM GLUCOSE CONCENTRATIONS INDUCE GLUCAGON COUNTERREGULATION IN HEALTHY NEWBORNS

Abstract

Before feeding regulatory mechanisms maintain blood glucose concentrations of the newborn to meet the demands of the central nervous system. The role of glucagon in this process has been investigated. Healthy, term babies without clinical signs of hypoglycemia were studied. A capillary blood sample was obtained at 3-15 hours (median 6 hours) of age, a second sample 24 hours later and serum concentrations of glucose, insulin and glucagon were measured. Glucose concentrations at the first sampling averaged 2.1 ± 0.5 mM (mean ± SD; n = 51) and were positively correlated with postnatal age. At the second sampling glucose concentrations had increased to 3.0 ± 0.5 mM. Glucagon concentrations were 541 ± 219 pg/ml at the first sampling and inversely correlated with glucose concentrations. At the second sampling glucagon concentrations had decreased to 406 ± 163 pg/ml. Insulin concentrations were 12.1 ± 2.4 and 10.6 ± 2.1 μU/ml, respectively, and did not correlate with glucose concentrations. In a multiple regression analysis glucose concentrations were inversely correlated with glucagon concentrations and positively correlated with birth weights but not correlated with insulin concentrations or other neonatal and maternal characteristics. The results suggest that glucagon is part of normal counterregulation against hypoglycemia and that neonatal energy stores, as indicated by birth weight, influence the ability to maintain normoglycemia.