508
UNIT THREE
Cortisol and related compounds are used as drugs to reduce inf
am-
mation. They relieve pain by
decreasing permeability oF capillaries, preventing leakage oF
f
uids that swell surrounding tissues
stabilizing lysosomal membranes, preventing release oF their
enzymes, which destroy tissue
inhibiting prostaglandin synthesis
The concentration oF cortisol compounds necessary to stif
e inf
am-
mation is toxic, so these drugs can be used For only a short time.
They are used to treat autoimmune disorders, allergies, asthma, and
patients who have received organ transplants or tissue graFts.
nal androgens), but some of them are converted into female
hormones (estrogens) by the skin, liver, and adipose tis-
sues. These hormones may supplement the supply of sex
hormones from the gonads and stimulate early development
of the reproductive organs. Adrenal androgens may also
play a role in controlling the female sex drive.
Table 13.11
summarizes the actions of the cortical hormones. Clinical
Application 13.3 discusses some of the effects of a malfunc-
tioning adrenal gland on health.
Cortisol’s actions help keep the blood glucose concentra-
tion within the normal range between meals. These actions
are important because just a few hours without food can
exhaust liver glycogen, another major source of glucose.
A negative feedback mechanism much like that con-
trolling the thyroid hormones T
3
and T
4
regulates cortisol
release. It involves the hypothalamus, anterior pituitary
gland, and adrenal cortex. The hypothalamus secretes CRH
(corticotropin-releasing hormone) into the hypophyseal por-
tal veins, which carry the CRH to the anterior pituitary gland,
stimulating it to secrete ACTH. In turn, ACTH stimulates the
adrenal cortex to release cortisol. Cortisol inhibits release of
both CRH and ACTH. As concentration of these substances
falls, cortisol production drops.
The set point of the feedback loop controlling corti-
sol secretion changes, adapting hormone output to chang-
ing conditions. For example, under stress—injury, disease,
extreme temperature, or emotional upset—nerve impulses
send the brain information concerning the situation. In
response, brain centers signal the hypothalamus to release
more CRH, leading to a higher concentration of cortisol until
the stress subsides
(f
g. 13.33)
.
Sex Hormones
Cells in the inner zone (zona reticularis) of the adrenal cor-
tex produce sex hormones. These hormones are male (adre-
Bloodstream
Hypothalamus
Higher brain centers
CRH
ACTH
Cortisol inhibits
secretion of CRH
and ACTH
Cortisol affects
various target cells
Stimulates
glucose
formation
Inhibits
protein
synthesis
Promotes
fatty acid
release
Cortisol
ACTH
stimulates
the adrenal
cortex to
release
cortisol
Release into
bloodstream
Stimulation
Inhibition
+
+
+
+
Anterior
pituitary
gland
FIGURE 13.33
Negative Feedback regulates cortisol secretion, similar to the regulation oF thyroid hormone secretion (see ±
g. 13.16).
(
+
= stimulation;
= inhibition)
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