Anemia of Chronic Kidney Disease
Erythropoietin is a hormone produced mainly in the kidneys, which stimulates the production and maintenance of red blood cells. As kidney function declines, whether from disease or aging, there is a steady decrease in kidney production of erythropoietin, and this is the primary etiology of anemia associated with chronic kidney disease.
Kidney function and glomerular filtration rate (GFR) (a measure of how well the kidneys filter blood) naturally decreases with age, and may be further decreased in the presence of chronic illnesses such as high blood pressure and diabetes, the two main causes of chronic kidney disease.
It can be hard to distinguish the effects of normal aging on the kidneys from chronic kidney disease. Although a decreasing GFR with age is considered normal, the diagnostic criteria for chronic kidney disease are not modified according to a patient's age. Chronic kidney disease is defined as kidney damage or a GFR less than 60 mL/minute/1.73 m2 for more than three months. It is further staged according to severity of GFR impairment and other symptoms.