In Vitamin D deficient rickets, which statement is true regarding 25(OH) vitamin D levels?

• A. Low 25(OH) vitamin D levels
• B. Elevated 25(OH) vitamin D levels
• C. Normal 25(OH) vitamin D levels
• D. Unknown 25(OH) vitamin D levels

Answer: (A)

Measuring 25-hydroxy vitamin D captures the body's vitamin D stores and is the standard indicator of vitamin D status. In vitamin D deficient rickets, those stores are depleted, so the circulating 25(OH) vitamin D level is low. The active form, 1,25-dihydroxy vitamin D, can be normal or even elevated in deficiency due to secondary hyperparathyroidism, but it does not reflect stored vitamin D and is not used to define deficiency. Therefore, the statement that 25(OH) vitamin D levels are low best fits the scenario. Elevated or normal levels would not align with deficiency.