Exocrine pancreatic function in cystic fibrosis.

Pancreatic dysfunction in cystic fibrosis (CF) begins in utero and, at birth, in most cases, cystic fibrosis is characterized by an elevated level of serum immunoreactive trypsin (IRT). If most patients with CF typically present insufficient pancreatic exocrine function, 10-15% of CF patients have pancreatic sufficiency and this status is genetically determined by one or two 'mild' mutations in CF transmembrane conductance regulator (CFTR). However, with age, these patients can develop pancreatic insufficiency.