Vitamin D deficiency is often a silent disease. In children with a severe vitamin D deficiency, the physical examination may reveal bowing in the legs. In adults with a severe vitamin D deficiency, the physical examination can reveal periosteal bone pain. This is best detected using firm pressure on the sternal bone or tibia.
Although not always required for the diagnosis of vitamin D insufficiency, a serum PTH level may be used to help establish the diagnosis of vitamin D insufficiency. Often, patients with vitamin D insufficiency have a corresponding elevated PTH, indicating secondary hyperparathyroidism. An inverse relationship exists between PTH and 25-hydroxyvitamin D levels.
Serum 25-hydroxyvitamin D level measurement is the best test to determine vitamin D status. Patients with a 25-hydroxyvitamin D level of < 30 ng/mL are considered vitamin D insufficient. A 25-hydroxyvitamin D level of < 20 ng/mL has been used to define vitamin D deficiency. The metabolite 1,25-dihydroxyvitamin D should not be used to measure vitamin D levels because levels can be increased by primary hyperparathyroidism.
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Cite this: Romesh Khardori. Fast Five Quiz: Vitamin D - Medscape - Jul 21, 2020.