Erythropoietin, known also as EPO, is a glycoprotein hormone that controls the production of red blood cells in a process called erythropoiesis. When the kidneys detect a lack of oxygen flowing through the bloodstream, they secrete this glycoprotein, increasing the production of red blood cells, the body’s primary method of transporting oxygen to tissues and muscles. Typically a human’s hematocrit level, the percentage of red blood cells in the bloodstream, is between 40 and 45. For most adult males, a hematocrit level of less than 42 is said to be anemic, meaning that red blood cells are in dangerously low supply; this number is substantially less for women.
Synthetic EPO is used to boost low hematocrit levels in chemotherapy patients and those suffering from kidney disease, who are unable to maintain the necessary levels without frequent EPO injections. Perhaps more famously, it is also used illicitly by many endurance athletes seeking to gain a competitive advantage by artificially increasing their red blood cell count. Traditionally, athletes have trained at high altitude to achieve a similar natural effect, but today more and more have chosen to artificially boost red blood cell activity through the use of synthetic EPO.
For all its negative publicity, synthetic EPO remains a positive medical advancement to treat anemia and prevent hypoxia, the condition in which tissues are deprived of oxygen. Researchers continue to improve the effectiveness of synthetic EPO and even to develop a new glycoprotein—called novel erythropoiesis-stimulating protein (NESP) —which eliminates several drawbacks of EPO in its current form. NESP not only requires smaller doses, but also lasts longer, eliminating the need for frequent and often-painful IV administration, which can have complications. Still, unlike the natural stimulus that occurs with the release of EPO, any artificial stimulus of red blood cell production has potential risks, as it raises hemoglobin to the desired levels above 15 grams per deciliter far too quickly. The body cannot properly adjust to the quick change in blood viscosity and substantial cardiac risk results. Given that risk, synthetic EPO must be highly regulated by the FDA so that its use is limited to medical necessity, not athletic performance enhancement.
1. According to the passage, which one of the following is a challenge in using synthetic EPO to treat patients?
(A) It has to be administered more frequently and in larger doses than is ideal.
(B) It does not increase hematocrit levels as quickly as naturally occurring EPO does.
(C) It has more cardiovascular risk than other treatments.
(D) It is frequently stolen by those seeking performance enhancement.
(E) It can result in dangerously low hematocrit levels.
2. Which of the following can be inferred about training at high altitude?
(A) It is not as effective as synthetic EPO at increasing red blood cells in an athlete.
(B) It does not allow athletes to reach levels of hemoglobin above 15 grams per deciliter.
(C) It increases hemoglobin levels in an athlete more slowly than synthetic EPO does.
(D) It poses no health risks to the athlete.
(E) It does not increase the viscosity of blood to a dangerous level.
3. All of the following are potential risks of synthetic EPO except that it ______ .
(A) can raise hemoglobin levels too quickly.
(B) increases hemoglobin to levels above 15 grams per deciliter.
(C) abruptly increases blood viscosity.
(D) increases the likelihood of cardiac problems.
(E) needs to be administered frequently.
4. Which of the following can properly be inferred from the passage?
(A) Training at high altitude is safer than using synthetic EPO.
(B) A higher percentage of athletes are using performance enhancing drugs than in the past.
(C) NESP is a more effective treatment for raising hematocrit levels than synthetic EPO.
(D) NESP carries fewer risks than synthetic EPO.
(E) Kidneys have some mechanism for monitoring oxygen levels.
参考答案：
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发表于 2021-6-30 08:43:56
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