Rav Endocrinology Vit D Defic

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* Vitamin D deficiency is characterized by

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* Vitamin D deficiency is characterized by a low-normal to mildly suppressed serum calcium level, mild hypophosphatemia, increased alkaline phosphatase and parathyroid hormone levels, and a decreased 25-hydroxy vitamin D level;

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best assesses body stores of the vitamin.

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measurement of the 25-hydroxy vitamin D level best assesses body stores of the vitamin.

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Measurement of 25-hydroxy vitamin D (calcidiol) is more informative than measurement of 1,25-dihydroxy vitamin D (calcitriol) in most patients with hypocalcemia because

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Measurement of 25-hydroxy vitamin D (calcidiol) is more informative than measurement of 1,25-dihydroxy vitamin D (calcitriol) in most patients with hypocalcemia because vitamin D deficiency causes hypocalcemia and stimulates parathyroid hormone secretion, which in turn stimulates renal conversion of 25-hydroxy vitamin D to 1,25-dihydroxy vitamin D

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a low serum 25-hydroxy vitamin D level. when...

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Low dietary intake, poor absorption of vitamin D, and lack of production in the skin will result in a low serum 25-hydroxy vitamin D level.

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25-hydroxy vitamin D level. will also be low in patients taking

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. This serum level will also be low in patients taking phenytoin, those with nephrotic syndrome (loss of vitamin D–binding protein), and those with hepatobiliary disease

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1,25-Dihydroxy vitamin D levels will be low despite normal or high 25-hydroxy vitamin D levels in patients with

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1,25-Dihydroxy vitamin D levels will be low despite normal or high 25-hydroxy vitamin D levels in patients with renal insufficiency, deficiency of renal 1α-hydroxylase (vitamin D–dependent rickets type 1), or hypoparathyroidism.

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Measurement of the patient’s serum alkaline phosphatase isoenzyme level does not specifically help diagnose vitamin D deficiency and is

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Measurement of the patient’s serum alkaline phosphatase isoenzyme level does not specifically help diagnose vitamin D deficiency and is probably unnecessary in this patient at high risk for vitamin D deficiency, hypocalcemia, and hypophosphatemia.

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Measurement of the osteocalcin level assesses

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Measurement of the osteocalcin level assesses bone formation. The level is elevated in disorders that increase the metabolic turnover of bone, such as Paget disease and osteomalacia. The serum level of osteocalcin is not a specific marker of vitamin D deficiency and is not indicated.

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Vitamin D deficiency is common, especially in older patients, and can mask the severity of

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Vitamin D deficiency is common, especially in older patients, and can mask the severity of primary hyperparathyroidism. In such patients, the parathyroid hormone level is disproportionately elevated compared with the serum calcium level, and urine calcium excretion is often normal, as with this patient. The 25-hydroxyvitamin D level reflects total body stores of vitamin D and is thus the most appropriate to measure; the 1,25-dihydroxy vitamin D level is influenced more by parathyroid hormone and phosphorus levels and by renal function.