Parathyroid hormone
Parathyroid hormone is responsible for the induction of increased calcium absorption in the gastrointestinal tract or gut and in the kidney. It also induces calcium and phosphate resorption from the bone by osteoclasts. Parathyroid hormone also plays a role in activating vitamin D from its pro form to its active form. Vitamin D is also responsible for increased blood calcium levels and works in conjunction with parathyroid hormone. Vitamin D is also partly responsible for the inhibition of parathyroid hormone release by binding Vitamin D receptors at the parathyroid gland.