[Glucose homeostasis in cystic fibrosis. Oral glucose tolerance test in comparison with formula administration]

Glucose tolerance is often impaired in Cystic Fibrosis. The impact of this condition on enteral nutritional support in case of malnourishment remains to be studied.

In this study the glucose-, C-peptide- and insulin-responses to an OGTT and a standard enteral formula load were investigated in 19 non-diabetic CF-patients. Each test was performed with a carbohydrate load of 1.75 g/kg bodyweight.

11 patients had a normal OGTT (Group I) and 8 had an impaired glucose tolerance (Group II). After the formula load the glucose concentrations were significantly lower than after the OGTT at 30, 60, and 90 min in both groups and at 120 min in group II only. In group II the glucose values exceeded 6.7 mmol/l at 120 min after both OGTT and formula load and were significantly higher than in group I. The food glycaemic index, a parameter for comparison of glucose response to different diets was calculated. It ranged from 30 to 80% in both groups. An increased C-peptide- and insulin-secretion was found in patients with impaired glucose tolerance.

The condition of impaired glucose tolerance must be considered for enteral hyperalimentation of Cystic Fibrosis-patients. The selection of formulas for nutritional support should be based on the calculation of the Food Glycemic Index because of its high interindividual variability.