Erythropoietin (cont.)
Chemically, what is erythropoietin (EPO)?
Erythropoietin is a protein with an attached sugar (a glycoprotein).
It is one of a number of similar glycoproteins that serve
as stimulants for the growth of specific types of blood
cells in the bone marrow.
What exactly does erythropoietin (EPO) do?
Erythropoietin stimulates the bone marrow to produce more
red blood cells. The resultant rise in red cells increases
the oxygen-carrying capacity of the blood.
As the prime regulator of red cell production, erythropoietin's
major functions are to:
- Promote the development of red blood cells.
- Initiate the synthesis of hemoglobin, the molecule
within red blood cells that transports oxygen.
Is the kidney the sole source of erythropoietin?
No. Erythropoietin is produced to a lesser extent by the liver. Only about 10% of the erythropoietin is produced in the liver. The
erythropoietin gene has been found on human chromosome 7 (in band
7q21). Different DNA sequences flanking the erythropoietin gene act to
control liver versus kidney production of erythropoietin.
Why is an erythropoietin test performed?
The erythropoietin hormone can be detected and measured in the
blood. The level of erythropoietin in the blood can indicate bone
marrow disorders, (such as polycythemia, or increased red blood cell production) kidney disease, or erythropoietin abuse. Testing erythropoietin
blood levels is thus of value if:
- Too little erythropoietin might be responsible for too few red blood cells (such as in evaluating anemia, especially anemia related to kidney disease).
- Too much erythropoietin might be causing too many red blood cells (polycythemia).
- Too much erythropoietin might be evidence for a
kidney tumor.
- Too much erythropoietin in an athlete may suggest erythropoietin abuse.
Next: How is the erythropoietin (EPO) test performed? »
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