The prevalence of overt diabetes mellitus and carbohydrate intolerance was studied in 448 patients with cystic fibrosis (CF). Insulin-dependent diabetes (IDDM) developed in 7.6% of patients (13 male and 21 female). Survival was significantly lower (P<0.01) in the IDDM-CF group, with fewer than 25% surviving to age 30 years, whereas nearly 60% of the nondiabetic CF population reached this age. A significant deterioration in CF clinical status, based on NIH score, became apparent 2 years before onset of overt IDDM (P<0.05 at 2 years prior, P<0.01 at IDDM diagnosis). Total glycosylated hemoglobin (HbA1) was significantly (P<0.001) higher for the total CF population (7.3%±1.2%) than for the general non-CF population (6.5%±0.7%), and in the IDDM-CF group, (P<0.05) compared with normoglycemic CF control patients. Female patients had a higher mean HbA1 after 12 years of age than their male counterparts did (P<0.02). HBA1 did not predict the development of IDDM, but there was a weak inverse relationship between HbA1 and both NIH clinical score (r=-0.41, P<0.02) and standard pulmonary function tests (forced vital capacity, r=-0.25, P<0.01) in the general CF population. Therefore, impaired carbohydrate tolerance in CF is associated with progressive clinical deterioration.
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Estimates of the frequency of diabetes mellitus in patients with cystic fibrosis range from 9% to 60%. 1,2 Evidence of impaired glucose tolerance is present in as many as 40% of patients with CF. Studies have also shown abnormalities in C peptide and glycosylated hemoglobin, with low insulin and glycogon reserves. 1-4 In contrast, in juvenile-onset insulin-dependent diabetes mellitus not associated with CF, C peptide is generally absent and glucagon response to hypoglycemia may be present early in the disease? In CF, loss of cells from the islets of Langerhans may parallel the Supported in part by Grant HL27355, from the National Institutes of Health, and by a grant from the American Diabetes Associati0n--Minnesota. Submltted for publication Jan. 9, 1987; accepted Sept. 22, 1987. Reprint requests: Stanley M. Finkelstein, PhD, Division of Health Computer Sciences, Department of Laboratory Medicine and Pathology, Box 511 UMHC, University of Minnesota, Minneapolis, MN 55455.