Calcitriol is a hormone produced in the body that plays an important role in regulating calcium and phosphorus levels. Calcitriol is also known as Vitamin D3. The hormone is primarily produced by the kidneys and is then further processed by the liver. It can be obtained from food sources like fish and mushrooms. Calcitriol is found in many medications, such as parathyroid hormone, calcitriol, and calcitonin.