Background: The unmodified frequently sampled intravenous glucose tolerance test (FSIGT) has not previously been used to assess insulin/glucose kinetics in patients with insulinoma.
Objective: To measure insulin sensitivity (Si) and glucose effectiveness (Sg) by means of the FSIGT in patients with insulinoma, before and after surgical removal of the tumour.
Subjects and methods: FSIGTs were performed in five patients, before and approximately 3 months post-surgery, and in 11 controls. Si and Sg were estimated using Minimal Model computer analysis of dynamic glucose and insulin data.
Results: Si was lower in insulinoma patients before, compared with after surgery (3.37 +/- 0.62 vs. 6.24 +/- 1.09 SE [x10(-4)] min(-1)microU(-1) ml, P < 0.05). Sg was similar in patients pre- and post-surgery (3.0 +/- 0.67 vs. 2.4 +/- 0.6 [x10(-2)] min(-1), NS).
Conclusions: Insulin sensitivity improves after excision of an insulinoma. Glucose effectiveness is not influenced by chronic hyperinsulinaemia and hypoglycaemia.