513
CHAPTER THIRTEEN
Endocrine System
13.1
FROM SCIENCE TO TECHNOLOGY
Treating Diabetes
T
he sweet-smelling urine that is the hall-
mark of type 1 diabetes mellitus was
noted as far back as an Egyptian papyrus
from 1500
B
.
C
. In
A
.
D
. 96 in Greece, Aretaeus of
Cappadocia described the condition as a “melting
down of limbs and F
esh into urine.” One of the ±
rst
people to receive insulin as a drug was a three-
year-old boy whose body could not produce the
hormone. In December 1922, before treatment,
he weighed only ±
fteen pounds. The boy rapidly
improved after beginning insulin treatment, dou-
bling his weight in just two months.
In 1921, Canadian physiologists Sir ²rederick
Grant Banting and Charles Herbert Best discov-
ered the link between lack of insulin and diabe-
tes. They induced diabetes symptoms in a dog by
removing its pancreas, then cured it by adminis-
tering insulin from another dog’s healthy pan-
creas. A year later, people with diabetes began to
receive insulin extracted from pigs or cattle.
In 1982, pure human insulin became avail-
able by genetically altering bacteria to produce
the human protein (recombinant DNA technol-
ogy). Human insulin helps people with diabetes
who are allergic to the product from pigs or cows.
Today, people receive insulin in several daily
injections, from an implanted insulin pump, and/
or in aerosol form (±
g. 13B).
Providing new pancreatic islets is a longer-
lasting treatment for type 1 diabetes. Islet cell
transplantation was ±
rst attempted in 1893, when
an English surgeon transplanted bits of a sheep’s
pancreas into an adolescent near death. He died a
few days later. After insulin was discovered, inter-
est in islet transplantation revived once research-
ers realized that the more frequent the daily doses
of insulin, the healthier the patient. Transplants
succeeded, in rats, in 1972. Difficulties arose,
however, in treating humans. It was challenging
to separate islets from cadaver pancreases, and
then collect enough beta cells, which account for
only 2% of pancreas cells. Many patients’ immune
systems rejected transplants. By the 1990s, auto-
mated islet isolation and new anti-rejection drugs
helped. In 1996 in Germany, and then in 1999 in
Edmonton, Canada, islet transplantation began.
Since 2000, several hundred people have
received islet transplants in a procedure called the
Edmonton protocol, which introduces islets into a
vein in the liver. By a year after transplant, from 50%
to 68% of patients do not need to receive additional
insulin, but by ±
ve years after the procedure, fewer
than 10% of total patients are free of daily insulin
supplementation. The procedure is risky—12%
of patients hemorrhage, and 4% develop blood
clots in the liver vein. These risks, plus the apparent
short-term improvement, have prompted physi-
cians to carefully evaluate which patients are most
likely to bene±
t from the few years of insulin inde-
pendence that the procedure may o³
er.
Researchers are currently investigating vari-
ous stem and progenitor cells to see if they can
be implanted to treat diabetes, using a patient’s
own cells. Reprogramming cells back to a stem-
like state might not be necessary—one research
group has succeeded in culturing pancreatic alpha
cells (from the digestive part of the pancreas) in a
way that stimulates them to give rise to beta cells.
A possible treatment for type 2 diabetes has
come from an unexpected place—gastric bypass
surgery, which removes parts of the stomach and
small intestine to help people lose weight. Isolated
reports since the 1950s noted cases of morbidly
obese people with diabetes having gastric bypass
surgery, and then, within days and with lasting
ect, not needing to inject insulin. By the 1980s,
doctors noticed
that some patients who had nor-
mal regulation of blood glucose before the surgery,
a few months after began to experience confusion,
altered behavior, seizures, and unconsciousness—
signs of low blood glucose. Today some surgeons
are performing gastric bypass surgery on people
who do not weigh as much as typical candidates for
the surgery, but who have severe diabetes. Treating
diabetes with weight-loss surgery is controversial,
because the mechanism of how it corrects blood
glucose regulation is not understood.
13.11
STRESS AND ITS EFFECTS
Because survival depends upon maintaining homeostasis,
factors that change the body’s internal environment are
potentially life threatening. Sensing such dangers directs
nerve impulses to the hypothalamus, triggering physiological
responses that resist a loss of homeostasis. These responses
include increased activity in the sympathetic division of
the autonomic nervous system and increased secretion of
adrenal hormones. A factor capable of stimulating such a
response is called a
stressor,
and the condition it produces
in the body is called
stress.
Other organs that produce hormones include the heart,
which secretes
atrial natriuretic peptide
(chapter 15, p. 556),
and the kidneys, which secrete
erythropoietin
that stimu-
lates red blood cell production (chapter 14, p. 527). Clinical
Application 13.1 discusses abuse of EPO to improve athletic
performance.
PRACTICE
44
Where is the pineal gland located?
45
What is the function of the pineal gland?
46
Where is the thymus gland located?
FIGURE 13B
A person with either common
form of diabetes mellitus must monitor his or
her blood glucose level and be very diligent
about proper diet and exercise.
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