Cystic-fibrosis-related diabetes mellitus is frequently underdiagnosed and associated with deterioration of overall clinical status. The purpose of this prospective study was to investigate the influence of insulin on nutrition, lung function and clinical status of cystic fibrosis patients. For a period of 5 y, and at 6-mo intervals, body mass index, forced expiratory volume in 1 sec, Shwachman score, intravenous glucose tolerance test and first-phase insulin response were determined in 30 cystic fibrosis patients (age range 10-35 y) with exocrine pancreatic insufficiency. During the study period, six patients (3M and 3F; age range 15-22 y) developed diabetes and required insulin therapy. The decrease of first-phase insulin response coincided with deterioration of nutritional and clinical status, which improved significantly 6 mo after the institution of insulin.
Conclusion: Insulin, as an anabolic hormone, could have an influence on body mass, which may affect pulmonary function and clinical condition in cystic fibrosis. It is important to identify cystic fibrosis individuals at risk of developing diabetes so that early insulin therapy is instituted.