Free 25-Hydroxyvitamin D Concentrations in Cystic Fibrosis
Moon Jeong Lee1, Malcolm D Kearns, Ellen M Smith
1Division of Endocrinology, Metabolism and Lipids (MJL, MDK, LH, TRZ, JAA, VT), Department of Medicine, Emory University, Atlanta, Georgia; Nutrition and Health Sciences Program (EMS, VT), Laney Graduate School, Emory University, Atlanta, Georgia; Atlanta Veterans Affairs Medical Center (VT), Section of Endocrinology, Atlanta, Georgia.
Background:
Vitamin D deficiency is common in cystic fibrosis (CF), but there is no previous data on free 25-hydroxyvitamin D (25[OH]D) in CF or in relation to healthy individuals.
Methods:
We assessed total serum 25(OH)D concentration by chemiluminescence and serum free 25(OH)D concentration by both direct measurement (ELISA) and calculation, using serum albumin and vitamin D binding protein (VDBP) levels in 80 subjects (28 healthy adults, 25 clinically stable adults and children with CF and 27 adults experiencing a CF exacerbation).
Results:
Serum albumin and VDBP concentrations were lower in CF compared with healthy controls. Total serum 25(OH)D concentrations were positively correlated with both calculated and measured free 25(OH)D (P < 0.001 for both). Calculated and directly measured serum free 25(OH)D levels were positively correlated (P < 0.001).
Conclusions:
Serum levels of directly measured free 25(OH)D positively correlated with total 25(OH)D, suggesting that achieving sufficient total serum 25(OH)D may result in adequate free 25(OH)D levels in CF.
Related Concept Videos
Cystic Fibrosis: Pathogenesis
CF is primarily caused by a genetic mutation in a chromosome 7 gene coding for the cystic fibrosis transmembrane conductance regulator (CFTR) protein. The most common gene mutation leading to CF is the ΔF508 mutation,...
Cystic Fibrosis: Management
Sinus disease and chronic...
Role of Skin in Vitamin D Synthesis
The solar UV B rays (290-315 nm) are absorbed by the skin, and 7-dehydrocholesterol (provitamin D3) photolyzes it to previtamin D3, which undergoes a rapid transformation to vitamin...


