CYP24A1 and Hypercalcemia: The resultant CYP24A1 protein inactivates the active form of vitamin D. This mechanism is crucial for maintaining constant plasma levels of active vitamin D. CYP24A1 dysfunction causes elevated plasma levels of 1,25(OH)2D3 and is associated with idiopathic infantile hypercalcemia or kidney stones, which indicates the importance of this enzyme for vitamin D metabolism (3, 4).