Chapter 6 The Endocrine System • MHR 197reaches from the ovary to the outside of the uterus.
The two fallopian tubestransfer an ovum from the
ovary to the uterus. The lining of each tube is
ciliated to create a current that moves the ovum
toward the uterus. The sperm fertilizes the ovum as
it travels down the fallopian tube. Ova are released
from different parts of the ovaries, so the openings
of the fallopian tubes consist of finger-like
projections called fimbriae, which sweep over the
ovaries. The fimbriae are also ciliated to sweep the
ovum into the fallopian tube for its trip to the uterus.
Cervical cancer occurs most often among women 30 to 50
years of age. A Pap test involves removal and examination
of cells from the cervix and vagina to determine the presence
of cancerous and pre-cancerous cells. Most cases of cervical
cancer are related to a sexually transmitted disease called
human papillomavirus (HPV).BIO FACT
Extra testosterone added to the body means less of the
following:
LH. This results in lower testosterone production in
men and disruption of the menstrual cycle in women.
testosterone. This leads to impotence and shrunken
testes.
follicle-stimulating hormone (FSH). This hormone is
responsible for the maturation of sperm and eggs.
Lower levels of FSH lead to sterility.Synthetic Steroids
Synthetic anabolic steroids were first developed in the
1930s. They were used medically to help the body:
rebuild tissues weakened by injury or disease,
regain weight after illness, and
recover more quickly from breast cancer and
osteoporosis.
By the 1940s, synthetic steroids were being used in
sports that relied on bulk and strength, such as weight
lifting, football, and shot-put. Steroid use soon spread to
other sports, and by the 1980s there was a growing
illegal market for steroids for non-medical purposes. The
International Olympic Committee lists over 17 anabolic
steroids and related compounds that are banned for use
by athletes in competition.
The synthetic steroids used by bodybuilders and athletes
are designed to mimic the anabolic traits of testosterone
while minimizing the androgenic or masculinizing effects.
To try to combat the unwanted effects produced by the
feedback loop, steroid users are increasingly sophisticated
with respect to the quantities of steroids they take and
the timing of use. As well, they often take several drugs in
combination, including other types of hormones, vitamins,
enzymes, and protein supplements.For example, DHEA (dehydrepiandosterone) is a natural,
weakly androgenic steroid hormone secreted by the
adrenal glands. It is converted in the body to
androstenedione (a testosterone-like hormone),
testosterone, or estrogen, depending on the user’s sex,
age, and physical condition. But attempts to influence
testosterone production in this way can also backfire.
DHEA can displace testosterone at androgen binding
sites, while enzymes convert excess DHEA to the female
sex hormone estrogen.Do They Work?
There are few reliable clinical studies on the long-term
effects of anabolic steroids and related drugs. With so
much still unknown, the regulations governing their use
and legality vary widely. What is freely sold as a harmless
food supplement in the United States may be illegal or
available only by prescription in Canada.
There are uncertainties and conflicting claims about the
benefits and dangers of steroids. However, a knowledge
of the body’s regulatory mechanisms suggests that long-
term use of hormones and other potent biological
molecules by a healthy individual is likely to have
cumulative harmful side effects. This is especially true of
young people, whose bodies are still developing. With a
balanced diet, rest, and exercise, most people have
sufficient levels of all the hormones they need.Follow-up
1.Make a sketch of the feedback loops governing the
production of testosterone by the testes.
2.One survey of professional athletes reported that
about half would be willing to take a drug that
ensured their success, even if it shortened their
lives. In groups, discuss the arguments for and
against the use of synthetic anabolic steroids by
athletes in competition.