509
CHAPTER THIRTEEN
Endocrine System
J
ohn F. Kennedy’s beautiful bronze complex-
ion may have resulted not from sunbathing,
but from a disorder of the adrenal glands.
When he ran for president in 1960, Kennedy
knew he had
Addison disease,
but his sta±
kept his
secret, for fear it would a±
ect his career. Kennedy
had almost no adrenal tissue but was able to
function by receiving mineralocorticoids and glu-
cocorticoids, the standard treatment.
In Addison disease, the adrenal cortex does
not secrete hormones su²
ciently due to immune
system attack (autoimmunity) or an infection
such as tuberculosis. Signs and symptoms include
decreased blood sodium, increased blood potas-
sium, low blood glucose level (hypoglycemia),
dehydration, low blood pressure, frequent infec-
tions, fatigue, nausea and vomiting, loss of appe-
tite, and increased skin pigmentation. Some
sufferers experience salt cravings—one woman
reported eating many bowls of salty chicken noo-
dle soup, with pickles and briny pickle juice added!
Without treatment, death comes within days from
severe disturbances in electrolyte balance.
An adrenal tumor or oversecretion of ACTH
by the anterior pituitary causes hypersecretion of
glucocorticoids (primarily cortisol), resulting in
Cushing syndrome.
It may also result from taking
corticosteroid drugs for many years, such as to
treat asthma or rheumatoid arthritis. Tissue pro-
tein level plummets, due to muscle wasting and
loss of bone tissue. Blood glucose level remains
elevated, and excess sodium is retained. As a
result, tissue ³
uid increases, blood pressure rises,
and the skin appears pu±
y. The skin may appear
thin due to inhibition of collagen synthesis by
the excess cortisol. Adipose tissue deposited in
the face and back produce a characteristic “moon
face” and “bu±
alo hump.” Increase in adrenal sex
hormone secretion may masculinize a female,
causing growth of facial hair and a deepening
voice. Other symptoms include extreme fatigue,
sleep disturbances, skin rashes, headache, and
leg muscle cramps.
Treatment of Cushing syndrome attempts to
reduce ACTH secretion. This may entail removing
a tumor in the pituitary gland or partially or com-
pletely removing the adrenal glands.
Both Addison disease and Cushing syndrome
are rare, and for this reason, they are often misdi-
agnosed, or, in early stages, the patient’s report of
symptoms is not taken seriously. Addison disease
ects thirty-nine to sixty people of every million,
and Cushing syndrome a±
ects ´
ve to twenty-´
ve
people per million.
13.3
CLINICAL APPLICATION
Disorders of the Adrenal Cortex
(f g. 13.34)
. It is attached to the f
rst section oF the small
intestine (duodenum) by a duct, which transports its diges-
tive juice into the intestine. The digestive Functions oF the
pancreas are discussed in chapter 17 (pp. 671–672).
The endocrine portion oF the pancreas consists oF cells
grouped around blood vessels. These groups, called
pancre-
atic islets
(islets oF Langerhans), include three distinct types
oF hormone-secreting cells—
alpha cells,
which secrete gluca-
gon;
beta cells,
which secrete insulin; and
delta cells,
which
secrete somatostatin
(f
gs. 13.34
and
13.35)
.
Hormones of the Pancreatic Islets
Glucagon
is a protein that stimulates the liver to break down
glycogen into glucose (glycogenolysis) and to convert non-
carbohydrates, such as amino acids, into glucose (gluconeo-
genesis). Glucagon also stimulates breakdown oF Fats into
Fatty acids and glycerol.
In a negative Feedback system, a low concentration oF
blood glucose stimulates release oF glucagon From the alpha
PRACTICE
35
Name the important hormones of the adrenal cortex.
36
What is the function of aldosterone?
37
What does cortisol do?
38
How are blood concentrations of aldosterone and cortisol regulated?
13.9
PANCREAS
The
pancreas
(pan
kre-as) consists oF two major types oF
secretory tissues. This organization oF cell types refl
ects its
dual Function as an exocrine gland that secretes digestive
juice through a duct and an endocrine gland that releases
hormones into body fl
uids.
Structure of the Gland
The pancreas is an elongated, somewhat Flattened organ
posterior to the stomach and behind the parietal peritoneum
TABLE
13.11
|
Hormones of the Adrenal Cortex
Hormone
Action
Factors Regulating Secretion
Aldosterone
Helps regulate the concentration of extracellular electrolytes by conserving sodium
ions and excreting potassium ions
Electrolyte concentrations in body ³
uids and
renin-angiotensin mechanism
Cortisol
Decreases protein synthesis, increases fatty acid release, and stimulates glucose
synthesis from noncarbohydrates
CRH from the hypothalamus and ACTH from the
anterior pituitary gland
Adrenal androgens
Supplement sex hormones from the gonads; may be converted into estrogens
previous page 539 David Shier Hole's Human Anatomy and Physiology 2010 read online next page 541 David Shier Hole's Human Anatomy and Physiology 2010 read online Home Toggle text on/off