<prompt> Which of the following is not the action of calcitriol?Calcitriol increases the intestinal absorption of calciumCalcitriol stimulates calcium uptake for deposition as calcium phosphate in the osteoblasts of boneCalcitriol increases the excretion of calcium and phosphate through the kidneyCalcitriol action is similar to steroid hormones  <response>: Calcitriol increases the intestinal absorption of calcium and phosphate. In the osteoblasts of bone, calcitriol stimulates calcium uptake for deposition as calcium phosphate, Thus calcitriol is essential for bone formation. Calcitriol is also involved in minimizing the excretion of calcium and phosphate through the kidney, by decreasing their excretion and enhancing reabsorption. Calcitriol action is similar to steroid hormones. lt binds to a receptor in the cytosol and the complex acts on DNA to stimulate the synthesis of calcium binding protein.Reference: Satyanarayana- Biochemistry, 3rd edition, pg-125 