25-Hydroxycholecalciferol levels in patients with cystic fibrosis.

Assessment of the status of circulating vitamin D in cystic fibrosis patients 
was investigated by determining serum levels of 25-hydroxycholecalciferol. The majority of 
the patients with CF and pancreatic insufficiency had levels of 25-OH-D 
within the normal range. Clinical symptoms or pathologic signs resulting from 
deficiencies of vitamins A and E in patients with CF have 
been repeatedly documented. In contrast, a paradoxical lack of vitamin D 
deficiency signs has been observed in CF patients. This is especially 
puzzling since rickets had been commonly associated with most other forms 
of steatorrhea. We can only speculate why rickets was formerly rarely 
reported in association with CF. Perhaps because of voracious appetites and 
the selective absorption of vitamin D via the lymphatics without requiring 
esterification, these individuals were spared clinical rickets. 