Evaluation of Glucose Tolerance and Insulin Treatment in Non Diabetic Patients With Cystic Fibrosis During Acute Pulmonary Exacerbation

The life expectancy of patients with cystic fibrosis (CF) has increased over the last decades due to improved understanding of the disease and new treatments. CF patients who live longer develop glucose intolerance and cystic fibrosis related diabetes (CFRD), in fact, routine annual screening by Oral Glucose Tolerance Tests (OGTT) shows that the prevalence of CFRD increases with age. CFRD is primarily an insulinopenic condition characterized by an impaired and delayed insulin secretion, as a consequence of fibrosis in the exocrine pancreatic tissue that compromises the ß-cell function.

The occurrence of CFRD is significantly related to increased morbidity and mortality. Based on data from the CF Patients Registry in the USA, the mortality rate of patients with CFRD is six-fold higher than that of patients without CFRD.

Our pilot study proved that during pulmonary exacerbation (PE), CF patients with Normal Glucose Tolerance (NGT) exhibited early latent diabetic glucose intolerance in Oral Glucose Tolerance Test(OGTT) which becomes completely normalized 3-4 weeks after resolution of PE. These patients who are considered to be normoglycemic may experience relatively long periods of hyperglycemia during recurrent events of pulmonary infections. Chronically increased glucose values during PE have an adverse impact on pulmonary function both during PE and in the long-term. Hyperglycemia may increase the duration and extent of recovery from PE. Furthermore it may impair the ability to overcome lung infections by directly stimulating the growth of respiratory pathogens. Finally, hyperglycemia per-se during stressful conditions may worsen the general outcome.

Insulin therapy is considered routine treatment for patients with CFRD. In addition to normalizing glucose levels, insulin has a beneficial effect on general pulmonary function and nutritional status, possibly due to its anabolic effect. No routine or formal guidelines for treating PE hyperglycemia are currently available. Normal Glucose Tolerance (NGT)patients, who are hyperglycemic during PE only, are generally not intensively treated for this condition, except if the treating physician decides on interventional insulin treatment. Some patients may experience relatively long periods of hyperglycemia during recurrent events of pulmonary infections.