The need of calcium in human body can be fulfilled by either absorption of calcium from the digested food or by reabsorption of calcium from renal tubules, which is stimulated by

Parathyroid hormone (PTH) increases the Ca2+ levels in the blood. PTH acts on bones and stimulates the process of bone resorption (dissolution / demineralisation). PTH also stimulates reabsorption of Ca2+ by the renal tubules and increases Ca2+ absorption from the digested food. PTH is a hypercalcemic hormone as it increases the blood Ca2+ levels.