Iguanas with demineralized bone are most likely deficient in which vitamin?

• A. Vitamin C
• B. Vitamin B12
• C. Vitamin E
• D. Vitamin D3

Answer: (D)

Demineralized bones in iguanas indicate metabolic bone disease driven by insufficient calcium absorption, which is tightly linked to vitamin D3. Vitamin D3 enables calcium (and phosphate) absorption from the gut and supports bone mineralization; when iguanas don’t get enough vitamin D3—either from diet or adequate UVB exposure—the gut can't absorb calcium efficiently, blood calcium falls, bone resorption increases, and bones become soft and demineralized. The other vitamins listed don’t directly drive calcium uptake and bone mineralization in this way: vitamin C is more about collagen synthesis, vitamin B12 relates to blood and nerve function, and vitamin E has antioxidant and other roles but not a primary effect on bone mineral density.