Toxicity of Vitamin D leads to hypercalcemia because it increases the intestinal absorption of calcium and promotes bone resorption. Excessive Vitamin D raises serum calcium levels, causing symptoms like nausea, vomiting, polyuria, and nephrocalcinosis. This hypercalcemic effect is unique to Vitamin D toxicity, distinguishing it from other vitamins. Management focuses on stopping Vitamin D intake and addressing hypercalcemia.

Reference: Harrison’s Principles of Internal Medicine, J. Larry Jameson et al., 20th Edition.