Serum concentrations of 25-hydroxyvitamin D and 24,25-dihydroxyvitamin D in patients with cystic fibrosis.

Steatorrhea is a prevalent gastrointestinal manifestation of cystic fibrosis. Although deficiencies of 
vitamins A, E, and K have been described in patients with 
this disease, vitamin D deficiency and rickets have rarely been reported. 
The major form of vitamin D, cholecalciferol (vitamin D3), is produced 
by ultraviolet irradiation of 7-dehydrocholesterol in the skin. Ergocalciferol (vitamin D2) 
is a product of plant ergosterol. We studied the vitamin D 
status of patients with cystic fibrosis by measurement of the serum 
concentrations of the major circulating metabolites of vitamin D: 25-hydroxyvitamin D 
and 24,25-dihydroxyvitamin D. The mean serum concentrations of total 25OHD, 25OHD3, 
and 24,25(OH)2D and 25OHD3/25OHD ratios in patients with cystic fibrosis were 
similar to values recorded in control subjects. The present study demonstrates 
that the serum concentrations of the major metabolites of vitamin D 
in patients with cystic fibrosis are similar to those in healthy 
subjects. 