Four-year follow-up of glucose tolerance and beta-cell function in nondiabetic cystic fibrosis patients.

Plasma glucose and insulin responses to oral glucose load were investigated and reinvestigated approximately 4 years later in 29 cystic fibrosis children and adolescents with initially normal fasting blood glucose levels. Patients' clinical status was evaluated at the time of both oral glucose tolerance tests. With respect to the basal test, the second one elicited blunted insulin responses and enhanced glycemic levels. Moreover, the prevalence of patients with diabetic glucose tolerance was significantly increased at the second evaluation and insulin secretion was markedly reduced in these patients. Deterioration of glucose tolerance and/or of insulin secretion over time was never accompanied by a significant worsening of clinical and/or nutritional status. In conclusion, in cystic fibrosis subjects with fasting euglycemia (a) both insulin secretion and glucose tolerance deteriorate during a 4-year follow-up, (b) an insulin secretion decrease is more evident in patients who develop diabetic glucose tolerance and (c) these metabolic changes are not significantly linked to a worsening of either nutritional or clinical parameters, even in the patients who develop diabetic glucose tolerance.