Although insulin-induced hypoglycemia is a potent stimulus for growth hormo
ne (GH) secretion in humans, hypoglycemia was reported to suppress GH in sh
eep. We investigated whether GH suppression in sheep during insulin hypogly
cemia resulted from the dose of insulin administered or the fed state of th
e animal. Saline or insulin (0.05, 0.2, 1.0, or 5.0 U/kg) intravenous bolus
es were administered to eight fasted ewes in a crossover experiment. In ano
ther experiment, four sheep were fed 2 h before intravenous administrations
of either 0.2 or 5 U/kg of insulin. All doses of insulin resulted in compa
rable hypoglycemia, although the duration of hypoglycemia increased directl
y with insulin dose. Hypoglycemia in fasted animals stimulated GH secretion
. The GH rise above baseline was inversely related to the insulin dose, and
the insulin doses of 1 and 5 U/kg resulted in late suppression of GH below
baseline concentrations. Insulin administration to fed animals caused an i
dentical degree of hypoglycemia but no increase in GH. Insulin-hypoglycemia
stimulates GH secretion in sheep in a manner similar to humans, and the re
sponse is dependent on both fed state and insulin dose.