And that's exactly why this is known as Erythropoietin, because it produces more Erythrocytes. Now, if we have more red blood cells inside our bloodstream, that means our oxygen level inside our blood will increase. So that means urethropoietin basically increases the amount of oxygen that is found inside our blood. Now, the second type of hormone released by our kidneys is calcitriol. And calcitriol is actually a lipid soluble hormone that is an active form of vitamin D. And what it basically does is it stimulates the increase in the calcium and phosphate ion concentration inside our blood. So this is basically used to control and regulate the amount of calcium found inside our blood.