title: Vitamin D metabolism and osteomalacia in cystic fibrosis.
abstract: A 25-yr-old black man with cystic fibrosis and cirrhosis developed symptoms of osteomalacia and hypocalcemia, hypophosphatemia, secondary hyperparathyroidism, and low circulating 25-hydroxyvitamin D (25-OHD). Serum 1,25-dihydroxyvitamin D (1,25-[OH]2D) was within the normal range. Iliac crest bone biopsy confirmed the diagnosis of osteomalacia. Oral administration of 50,000 IU of vitamin D2 failed to relieve symptoms or raise serum 25-OHD levels to normal. Intramuscular vitamin D2, 10,000 IU every 8-12 week, improved symptoms, raised serum 25-OHD to normal, and increased circulating 1,25-[OH]2D to values five times normal. Over the next 10 mo circulating 1,25-[OH]2D remained elevated despite normalization of serum calcium, phosphorus, and parathyroid hormone. Repeat bone biopsy 1 yr after parenteral vitamin D showed healing of the osteomalacia. Malabsorption of vitamin D appears secondary to profound steatorrhea due to pancreatic insufficiency and secondary biliary cirrhosis. Although extensive hepatocellular disease was present, hepatic conversion of vitamin D to 25-OHD was intact. Both high and low circulating 1,25-[OH]2D levels during active osteomalacia have been reported; initially, the level was in the normal range and higher values in this patient occurred with repletion of 25-OHD substrate. This study shows that symptomatic osteomalacia may be a major manifestation of cystic fibrosis in those patients surviving into adulthood. Measurements of serum 25-OHD in cystic fibrosis patients may identify those who should receive supplemental vitamin D.
mesh_terms: D000328:Adult; D001842:Bone and Bones / Q000473:pathology; D002118:Calcium / Q000378:metabolism; D003550:Cystic Fibrosis / Q000188:drug therapy / Q000378:metabolism*; D004872:Ergocalciferols / Q000627:therapeutic use; D006801:Humans; D006887:Hydroxycholecalciferols / Q000097:blood; D006962:Hyperparathyroidism, Secondary / Q000378:metabolism; D006996:Hypocalcemia / Q000378:metabolism; D008099:Liver / Q000378:metabolism; D008103:Liver Cirrhosis / Q000378:metabolism; D008274:Magnesium / Q000378:metabolism; D008286:Malabsorption Syndromes / Q000378:metabolism; D008297:Male; D010018:Osteomalacia / Q000188:drug therapy / Q000378:metabolism*; D010281:Parathyroid Hormone / Q000097:blood; D010758:Phosphorus / Q000097:blood; D012709:Serum Albumin / Q000032:analysis; D014807:Vitamin D / Q000378:metabolism*
chemical_list: D004872:Ergocalciferols; D006887:Hydroxycholecalciferols; D010281:Parathyroid Hormone; D012709:Serum Albumin; D014807:Vitamin D; D010758:Phosphorus; D008274:Magnesium; D002118:Calcium