The Assay of Vitamin D and Its Metabolites

Recently a multiple assay procedure for determination of all the metabolites of vitamin D has been described ° A flow sheet of the analysis is shown in Fig. 7. Plasma vitamin D metabolite levels in normal and anephric human subjects are shown in Table, 1. 

Straight phase HPLC Zorbax SIL 10 90 isopropanol hexane 

8 Use of Vitamin D Metabolites in Treatment of Disorders of Bone and Caldum Metabolism 

It is obvious that a variety of disorders would result from a disturbance of the vitamin D endocrine system. Fat malabsorption would result in a deficiency of vitamin D giving rise ultimately to osteomalacia or rickets or secondary hyperparathyroidism. A hepatic disorder such as severe cirrhosis, or biliary atresia, may result in malabsorption of vitamin D and defective vitamin D-25-hydroxylation. Dilantin and phenobarbital cause low plasma 25-OH-D levels resulting in rickets and osteomala-cia246) Qf parathyroid glands would cause a severe hypocalcemia and tetany. 

Kidney failure results in severe secondary hyperparathyroidism, osteomalacia and osteosclerosis These patients cannot produce 1,25-(OH)2D3 when in need of calcium. Vitamin D dependency rickets is likely a defect in 25-OH-D-la-hydroxyla-tion Osteoporosis may in part result from inadequate l,25-(OH)2D3 production and thus inadequate calcium absorption resulting in loss of bone  

---