Insulin sensitivity and beta-cell function assessed by C-peptide in young adults with cystic fibrosis

Eight patients with cystic fibrosis (CF) aged 18-34 who had normal random plasma glucose levels were studied with a continuous infusion of glucose with model assessment (CIGMA) and plasma C-peptide to assess beta-cell function, and plasma insulin to assess insulin sensitivity. Two had impaired glucose tolerance, two had impaired beta-cell function and all had normal insulin sensitivity. The results of previous studies suggesting that glucose intolerance is common in CF may reflect the inability of an impaired liver to handle a large oral glucose load. The few CF patients who become diabetic may be those who have a preexisting diabetic trait.