Early detection of impaired glucose tolerance in patients with cystic fibrosis and predisposition factors

Introduction: The number of patients with glucose tolerance alterations ass ociated with cystic fibrosis (CF) has increased, probably due to the greate r survival rate among sufferers of this disease. We studied impaired glucos e tolerance (IGT) in patients with CP and investigated whether its appearan ce has any relationship with age, sex, genetic mutation and/or the degree o f clinical involvement. We assessed the parameters that might allow early d etection. Patients ann Methods: In 28 patients with CF (14 M, 14 F; aged 22 months to 18 years), sex, genetic mutation, nutritional status and the degree of pan creatic and pulmonary involvement were recorded. The metabolic study includ ed glycosylated hemoglobin (HbA(1c)) determination, oral glucose tolerance test (OGTT) and intravenous glucose tolerance tests (IVGTT). Results: In the patients with CF, 35.71% showed impaired glucose tolerance (IGT) and 3.57% had diabetes mellitus. The patients with IGT and CP were 3. 2 years older than those with normal glucose tolerance (NGT; p<0.05), but n o significant differences were found regarding sex, anthropometric measurem ents, percentage of pulmonary gammagraphic involvement, Shwachman-Kulczycki test or HbA(1c). In the OGTT, the patients homozygous for the <Delta>F508 mutation had higher blood glucose values than the heterozygous group (p=0.0 3), but these values were not higher than those in patients with other-muta tions. During the OGTT, blood insulin values at 30' were reduced in patient s with IGT compared to patients with NGT (p<0.02) and the insulin peak occu rred at 100.9 +/- 24.3 min compared to 65.3 +/- 21.8, respectively (p<0.05) . In the IVGTT, 82.14% of the patients had reduced insulin levels at 1 and 3 min (I1'+3'). No differences in the blood glucose levels during the OGTT were found between patients with normal I1'+3' values and patients with red uced values. Conclusions: A high percentage of patients with CP also present with IGT. T his increases with age and is more common among patients homozygous for the Delta F508 mutation and is not related to clinical status. Alterations in the kinetics of insulin secretion play an important role in the appearance of IGT and CF. We suggest that the OGTT is a more sensitive method than IVG TT for identifying early alterations in CF-related diabetes mellitus.