OBJECTIVES Insulin is believed to be the prime regulator of insulin-li
ke growth factor binding protein 1 (IGFBP-1) secretion, and in normal
subjects acute insulin induced hypoglycaemia exerts a rapid effect on
concentrations of IGFBP-1, and may also influence insulin-like growth
factor I (IGF-I) concentrations. The rise in IGFBP-1 concentrations in
normal subjects following hypoglycaemia has been suggested to be due
to suppression of endogenous Insulin secretion. We have examined this
further by studying diabetics with no endogenous insulin secretion. DE
SIGN We have compared the IGFBP-1 response to acute insulin induced hy
poglycaemia in normal subjects and patients with Type 1 (insulin depen
dent) diabetes mellitus. METHODS Insulin tolerance tests were performe
d using a bolus of insulin (0.15 U/kg), in six control subjects and si
x patients with Type 1 diabetes. MEASUREMENTS Serum levels of IGFBP-1,
insulin, glucose, and IGF-I were measured at regular intervals during
the insulin tolerance test. RESULTS Blood glucose fell to a nadir whi
ch coincided with the onset of the acute autonomic reaction 'R' in bot
h groups. The basal concentration of IGF-I was significantly lower in
the diabetic group at 0.4 +/- 0.1 kU/l, compared to 0.9 +/- 0.1 kU/l i
n the control group, but there was no significant change in IGF-I conc
entrations in response to hypoglycaemia in either group. Hypoglycaemia
provoked a fall in IGFBP-1 in patients with Type 1 diabetes, from 38
+/- 9 mu g/l basally to 17 +/- 3 mu g/l at R + 120 minutes, with a ret
urn to basal values of 45 +/- 11 mu g/l at R + 180 minutes. In the con
trol subjects there was no fall in IGFBP-1, but a significant increase
to 71 +/- 14 mu g/l at R + 180 minutes. CONCLUSION This difference in
the IGFBP-1 response in the presence of a similar glucose response su
ggests that in Type 1 diabetes there may be different sensitivities to
the actions of exogenous insulin on IGFBP-1 regulation.