Serum immunoreactive trypsin and pancreatic lipase in cystic fibrosis.

Serum immunoreactive trypsin (IRT) and pancreatic lipase have been measured in 59 patients with cystic fibrosis (age 1 month-27 years). Follow-up values were obtained from 49 patients. Their serum enzyme levels were compared to those of 120 healthy children of all age groups. Faecal fat excretion was determined in selected patients (n = 23) to elucidate the relationship between serum enzyme levels and pancreatic exocrine function. In cystic fibrosis IRT and lipase showed a very similar age-correlated pattern: in infancy levels were markedly elevated. During the following years the concentrations of both enzymes decreased rapidly and were found to be far below the normal range after the 10th year of life. Elevated enzyme levels in infancy as well as low levels in all age groups coincided with steatorrhea. Older patients (11-27 years) without severe pancreatic insufficiency however, had IRT and lipase levels in or above the normal range. In healthy children there was no age dependency of IRT levels, whereas in the first 12 months of life lipase levels were significantly lower than in later childhood.