Insulin Secretion, Glycosylated Haemoglobin and Islet Cell Antibodies in Cystic Fibrosis Children and Adolescents with Different Degrees of Glucose Tolerance

Summary

In comparison with 12 weight-matched controls, 39 children and adolescents with cystic fibrosis (CF) showed higher fasting glycaemic levels and both delayed and enhanced blood glucose responses to OGTT. Glycaemic response was normal in 30/39 patients (76.9%), impaired in other 7 cases (18%) and diabetic in the remnant two (5.1%). Fasting insulin levels and total insulin output during OGTT did not differ in patients and controls, but insulin peak in CF group was delayed and sustained. In the whole CF series mean HbA_1c was higher than in controls but no difference was found between patients with normal and those with impaired glucose tolerance. Islet cell antibodies were absent in the entire CF group. In conclusion, our results confirm the raised prevalence in CF of glucose tolerance abnormalities, which do not seem to depend on autoimmune factor involvement. Delayed insulin response to OGTT can be considered a very early expression of beta cell impairment in the course of CF. In our experience HbA_1c assay did not constitute a sensitive and specific screening test for detection of the C patients with glucose intolerance.

Key words

Cystic Fibrosis - Glucose Intolerance - Insulin Secretion - Glycosylated Haemoglobin - Islet Cell Antibodies - Beta Cell Impairment