B-cell function in thalassemia major
Hepatic and pancreatic damage owing to iron overload is often present in patients with beta-thalassemia major. In order to investigate B-cell function and hepatic insulin clearance in these patients, under a high transfusion program and regular chelation therapy, we studied the glucose (BG), insulin (IRI) and C-peptide (CPR) response and the CPR/IRI ratio after OGTT in 27 patients with Cooley's anemia and in 10 sex- age- and weight-matched healthy subjects; we also studied BG and IRI levels after IVGTT in 9 beta-thalassemic patients and in 9 control subjects. Furthermore, BG, CPR, IRI and glucagon (IRG) response to arginine infusion were evaluated in 5 thalassemic patients with normal OGTT and in 5 age-, sex- and weight-matched normal children, in order to assess pancreatic A-cell function, too. OGTT and IVGTT were normal in the patients with beta-thalassemia major. Plasma IRI level 30 min after an oral glucose load and the insulinogenic index for cumulative intervals were significantly lower in thalassemics after OGTT, whereas the insulin response and insulinogenic index were normal following i.v. glucose. No significant difference was observed for the CPR/IRI ratio during OGTT between thalassemics and normal subjects. Finally, BG, CPR, IRI and IRG levels were similar in the thalassemic patients and in healthy children both fasting and following arginine infusion. Our data suggest that patients with beta-thalassemia major, under a high transfusion program and regular chelation therapy, may have normal glucose tolerance and normal hepatic insulin clearance in spite of iron overload in pancreas and liver. Insulin response to oral glucose was lower than the one to IVGTT, probably because of diminished secretion of the gastrointestinal hormones which stimulate insulin release.