The total calcium balance is regulated by PTH, 1,25(OH)2D3, and calcitonin through their interaction with the kidneys, bones and gastrointestinal tract [10]: a reduction in serum calcium induces PTH and 1,25(OH)2D secretion, increasing both its renal retention and intestinal absorption, whereas hypercalcemia is counterbalanced by calcitonin secretion and PTH inhibition. Here, CALCA is linked to Hypercalcemia.