In addition to removing wastes, your kidneys release three important hormones:
erythropoietin (eh-RITH-ro-POY-eh-tin), or EPO, which stimulates the bone marrow to make red blood cells
renin (REE-nin), which regulates blood pressure
calcitriol (kal-suh-TRY-ul), the active form of vitamin D, which helps maintain calcium for bones and for normal chemical balance in the body.
You will have serious health problems if you have less than 25 percent of your renal function. If your renal function drops below 10 to 15 percent, you cannot live long without some form of renal replacement therapy?either dialysis or transplantation.
Why do kidneys fail?
Most kidney diseases attack the nephrons, causing them to lose their filtering capacity. Damage to the nephrons may happen quickly, often as the result of injury or poisoning. But most kidney diseases destroy the nephrons slowly and silently. Only after years or even decades will the damage become apparent. Most kidney diseases attack both kidneys simultaneously.
The two most common causes of kidney disease are diabetes and high blood pressure. If your family has a history of any kind of kidney problems, you may be at risk for kidney disease.
Most kidney problems happen slowly. You may have ?silent? kidney disease for years. Gradual loss of kidney function is called chronic kidney disease (CKD) or chronic renal insufficiency. People with CKD may go on to permanent kidney failure. They also have a high risk of dying from a stroke or heart attack.
More info at:
http://kidney.niddk.nih.gov/kudiseas...neys/index.htm
A short bit on blood production.
http://www.pbs.org/wnet/redgold/basi...roduction.html