Serotonin metabolism in cystic fibrosis.

The average blood serotonin level of 67 children with cystic fibrosis was 
found to be about twice that of age-matched normal children. There 
was no corresponding increase in the urinary excretion of 5- hydroxyindoleacetic 
acid (5-HIAA). Children with cystic fibrosis were well able to metabolize 
serotonin taken by mouth. No significant correlations were found between the 
blood serotonin level and the platelet count, height, weight, skinfold thickness, 
and pulmonary function test, 5 out of 44 patients had raised 
serum IgE levels, and their mean blood serotonin was higher than 
in those with normal IgE levels. No explanation for this emerged. 
Comparable findings (raised blood serotonin normal platelet count, normal urinary 5-HIAA) 
have been reported only in severe mental retardation. Further study of 
this phenomenon is warranted because (a) a raised blood serotonin level 
is sufficiently characteristic of cystic fibrosis to explore its use in 
diagnosis, and (b) it may help to explain the pathogenesis of 
cystic fibrosis and (c) the metabolism and function of serotonin. 