Examination of a 5-year-old child with a hereditary kidney disorder has detected signs of rickets, though the child's laboratory tests show normal vitamin D levels. What is the most likely cause of rickets in this case?

• A. Hyperparathyroidism
• B. Increased calcium excretion
• C. Insufficient calcium intake with food
• D. Impaired calcitriol synthesis
• E. Hypoparathyroidism