Medical Associates Clinic

 Quality Care Close To Home

Gettysburg Medical News
 The Clinical View
 by P.E. Hoffsten, MD
 22 March 2006

WHAT IS ERYTHROPOIETIN?

            My sincere apologies for this great big word that probably very few people have even heard of unless you are in the medical profession.  But a patient came in last week and had written this word down on a piece of paper.  She said that her mother was having cancer chemotherapy and was getting very anemic.  The doctor taking care of her had prescribed erythropoietin shots to help build her blood back up.  My patient wanted to know why her mother couldn’t just take an iron pill to build up her blood.  She said that the erythropoietin shots were terribly expensive and not completely covered by her insurance.

            To begin with, it would help to understand a little bit about anemia.  The normal human blood appears as a uniform red liquid.  But if it is allowed to clot, one can see that there is soon a separation into a clear amber fluid that looks like beer and a red blood clot part.  The red blood clot part generally makes up around 45% of the total volume of blood and the clear serum makes up about 55% of the normal blood volume.  A person is said to be anemic if the percentage of red cells drop below about 42% for men or around 37% for women.  Just naturally, women seem to have a little less red cell mass then men do.  So basically anemia means not enough red blood cells.

            The next question to consider is what causes anemia.  There are really only two things that can go wrong.  First, the person might not be making enough red blood cells or secondly, they may be losing too many.  The most common cause of anemia in an adult is bleeding losing blood into the bowel.  Very frequently the blood is not seen in the stool and the person can become very anemic before the problem is ever discovered.  This is a common presenting symptom for people with cancer of the colon or with ulcers.  Replacing iron can help the bone marrow have enough iron to keep up with blood production even though unknown bleeding is occuring.  But this hides the bleeding for a prolonged period of time.  A normal adult diet should have enough iron it to support a person’s normal needs.  The use of iron pills on a routine basis is probably not that good of an idea.  It may hide bleeding until the cause is very late in its course.

            The other cause of anemia is when the bone marrow, which makes blood, has something wrong and can’t keep up with normal daily blood turnover.  Blood production is dependent upon three things.  First, there must be enough raw materials such as iron, Vitamin B12, niacin, and protein.  Second, there has to be the normal blood-making cells present.  Patients with leukemia, or some cancers where the bone marrow cells are crowded out by cancer cells, become anemic because there just aren’t enough blood-making cells.  But, if there are enough raw materials and enough blood-making cells, a very common cause of anemia is that the blood-making cells are simply not directed to make blood.  Believe it or not, there is a hormone that is made in the kidney called erythropoietin that tells the bone marrow to make blood.  When the blood count drops a little bit, the kidney makes more erythropoietin telling the bone marrow to spiff it up and get going.

            The word erythropoietin looks like a big cumbersome word but it is relatively simple.  The first part is “erythro”, a medical term pertaining to red blood cells.  In some medical terms, it means “red” but in the case of erythropoietin it means pertaining to red blood cells.  The second half of the word “poietin” pertains to “production of”.  Thus erythropoietin is a hormone made by the kidney that tells the bone marrow to make more red cells.

            In modern medical care, erythropoietin is used for people that have chronic illness, or are undergoing chemotherapy, or have chronic kidney disease.  Patients with chronic kidney disease don’t have normal kidneys to make erythropoietin,so the person becomes anemic for that reason.  Their anemia can be completely reversed with this hormone.  But in people that are chronically ill or on chemotherapy, their kidneys simply don’t make enough erythropoietin; we don’t really understand why.  But we can supplement the person with this hormone and build their blood count back up to help them feel better and deal with their disease process.  Thus if a person is on chemotherapy, giving more iron isn’t going to do a thing but erythropoietin may help.

            The story of how this hormone became commercially available is quite remarkable by itself.  The hormone was first isolated 20 or more years ago.  But then the research scientists not only isolated the hormone, they found the genetic DNA sequence on how to make it.  They took that DNA genetic sequence and incorporated it into the genetic material of bacteria.  Bacteria can grow a lot in a hurry.  Pretty soon there were barrels of these bacteria producing erythropoietin.  To be sure, the material had to be purified to get the bacteria away from the hormone, but this can be done.  Before you know it, they had erythropoietin in a bottle that can be injected into a person and help them make blood when they aren’t making enough for themselves.  When the product was first marketed, it required daily injections.  Pretty soon, we learned that it only took an injection 2 or 3 times a week and now there are new preparations that require an injection only once every week or every two weeks.  It is not out as a pill yet but may be some day.  This technology is also the way insulin is provided today.

            I have mentioned before that every once in awhile, these medical science guys get something really right.  Erythropoietin is very good example of just how clever these people are.