LISA CLARK: One of those is the production of red blood cells. I wasn't aware that the kidneys worked in that function, as well.
JAI RADHAKRISHNAN, MD: This is correct, because one assumes that the red blood cells are there and you take it for granted, but what controls the number of red cells? So the kidney has sensors that look at the oxygen content of the blood flowing through the kidney, and if it detects that the oxygen concentration is low, it makes a hormone called erythropoietin, which increases the bone marrow's production capacity to make more red cells. For example, if you lose a lot of blood, there's a drop in the oxygen going to the kidney as a consequence of the depletion of these red cells, and there's an immediate increase in the production of this hormone, erythropoietin.
LEONARD STERN, MD: The hormone level is critically important in people with normal kidney function, and people who have failing kidneys don't make this hormone, so one of the features of chronic kidney disease is the anemia that develops, and the patients feel horribly fatigued and they're dysfunctional because they're unable to make these red blood cells. A nice part about our pharmaceutical industry is they have cloned the genes to make this hormone, and this is a medication that we now have available that we can give as a replacement.
LISA CLARK: Now, there is also another hormonal activity that goes on in the kidneys. Tell me a little bit about that.
