489
CHAPTER THIRTEEN
Endocrine System
amphetamines spread to the sports world. Today,
the general focus of performance enhancement
is misuse of certain powerful hormones of the
endocrine system. Three types of approaches are
described here.
Steroids
Athletes who abuse steroids seek the hormone’s
ability to increase muscular strength. They are
caught when the steroids or their metabolites are
detected in urine or when natural testosterone
levels plummet in a negative feedback response
to the outside supply of the hormone.
Steroids are powerful drugs, and abus-
ing them carries serious risks to health. Steroids
hasten adulthood, stunting height and causing
early hair loss. In males, excess steroid hormones
lead to breast development, and in females to a
deepened voice, hairiness, and a male physique.
The kidneys, liver, and heart may be damaged,
and atherosclerosis may develop because ste-
roids raise LDL and lower HDL—the opposite of
a healthy cholesterol profile. Steroids can also
cause psychiatric symptoms, including delusions,
depression, and violence.
For some athletes, illicit steroid use cannot
be detected because of a natural mutation that
deletes part of a gene. The result is a block in the
conversion of testosterone from fat soluble to
water soluble, and the hormone is not excreted
into the urine as it normally is. This mutation is
responsible for variations seen in di±
erent popu-
lations in the amount of urinary testosterone
excreted. In one telling experiment, researchers
in Sweden injected ²
fty-²
ve male volunteers with
a high dose of testosterone—and seventeen of
the men showed no traces of the steroid in their
urine! The ratio of testosterone to epitestosterone
(synthesized together) serves as a test of taking
exogenous testosterone. The body produces tes-
tosterone and an inactive form of it, called epi-
testosterone, in about equal amounts. An amount
of testosterone in great excess of the amount of
epitestosterone therefore indicates “doping.” In the
study, the men without the mutation had a T:E of
100, reflecting their massive doses. Men missing
I
t is di³
cult to keep up with the numbers of
athletes, amateur and professional, caught
using performance-enhancing drugs. In
late 1999 the International Olympic Committee
founded the World Anti-Doping Agency to set
rules and regulations, but it has not stopped
the problem. At the summer games in Sydney,
Australia, in 2000, the first time the agency par-
ticipated, thirty-six athletes and coaches were dis-
missed for breaking the new rules. Four years later,
at the summer games in Athens, six medals were
revoked. By 2008, the agency released an updated
list of banned drugs (table 13A). Famous athletes
are often caught too, as baseball hero Barry Bonds
and sprinter Marion Jones discovered.
Athletes have used drugs to aid perfor-
mance since the earliest Olympics, when cocaine,
heroin, morphine, and strychnine were the drugs
of choice. During World War II, soldiers took
amphetamines to mask the fatigue that accom-
panies great exertion. Shortly after the war, use of
one copy of the gene had a T:E of 50, and those
missing both copies of the gene had a T:E of 0 to 4.
Growth Hormone
Some athletes take human growth hormone
(HGH) preparations to supplement the e±
ects of
steroids, because HGH enlarges muscles, as ste-
roids strengthen them. HGH has been available
as a drug since 1985, and it is prescribed to treat
children with certain forms of inherited dwar²
sm.
However, HGH is available from other nations
and can be obtained illegally to enhance athletic
performance. Unlike steroids, HGH has a half-life
of only seventeen to forty-five minutes, which
means that it becomes so scant that it is unde-
tectable in body fluids within an hour. (Half-life
is the time that it takes half of a given number of
particles to break down into another substance.)
Erythropoietin
Increasing the number of red blood cells can
increase oxygen delivery to muscles and thereby
enhance endurance. Swedish athletes introduced
“blood doping” in 1972. The athletes would have
blood removed a month or more prior to perfor-
mance, then have the blood reinfused shortly
before a competition, boosting the red blood cell
supply. Easier than blood doping is to take eryth-
ropoietin (EPO), a hormone secreted from the
kidneys that signals the bone marrow to produce
more red blood cells. EPO is used to treat certain
forms of anemia. Using it to improve athletic per-
formance is ill advised. In 1987, EPO abuse led
to heart attacks and death in twenty-six cyclists
from the Netherlands. Runners and swimmers
also use EPO.
Testing for drugs or for mutations that
enable athletes to mask abuse is expensive. While
geneticists and biochemists sort out natural
nuances in the metabolism of these substances,
sports officials are using an “athlete’s passport”
to try to expose use of performance-enhancing
drugs. The passport is a record of drug test results
taken over several years, against which new drug
activity is detectable.
13.1
CLINICAL APPLICATION
Using Hormones to Improve Athletic Performance
TABLE
13A
|
List of Prohibited
Drugs
Anabolic agents
Anabolic androgenic steroids
Other anabolic agents
Hormones and related substances
EPO
Growth factors
Gonadotropins (LH, hCG in males)
Insulin
Corticotropins
Beta-2 agonists
Hormone antagonists and modulators
Aromatase inhibitors
Selective estrogen receptor modulators
Other antiestrogens
Myostatin inhibitors
Diuretics
Source:
World Anti-Doping Agency
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