Reduced serum 25-hydroxyvitamin D concentration and disordered mineral metabolism in patients with cystic fibrosis.

Vitamin D and mineral metabolism were studied in 21 adolescents and young 
adults with cystic fibrosis and the results were compared to those 
in 21 matched controls. All CF patients had been maintained on 
standard multivitamin supplements in combination with pancreatic enzyme replacement. Despite this 
supplementation, relative to control subjects the CF patients had a 36% 
reduction in serum 25- hydroxyvitamin D concentration, a slight but significant 
reduction in serum calcium concentration, evidence of calcium malabsorption with secondary 
hyperparathyroidism, and a 14% decrease in bone mass measured by the 
photon absorption technique. Currently accepted modes of pancreatic enzyme replacement and 
vitamin D supplementation are often inadequate to maintain normal mineral homeostasis 
in CF patients; additional measurements may be required to reduce the 
risk of clinically significant osteopenia concomitant with prolonged survival in CF. 
