Chapter 16
The Endocrine System
615
16
estrogens produced afer menopause when ovarian estrogens
are no longer produced. Control oF gonadocorticoid secretion is
not completely understood. ACTH stimulates their release, but
the gonadocorticoids do not appear to exert Feedback inhibition
on ACTH release.
Homeostatic Imbalance
16.8
Since androgens predominate, hypersecretion oF gonado-
corticoids causes
adrenogenital syndrome
(masculinization).
In adult males, elevated gonadocorticoid levels may not be
noticeable since testicular testosterone has already produced
masculinization, but in prepubertal males and in Females, the
results can be dramatic. In boys, the reproductive organs ma-
ture and secondary sex characteristics appear early, and the
sex drive emerges with a vengeance. ±emales develop a beard
and a masculine distribution oF body hair, and the clitoris
grows to resemble a small penis.
The Adrenal Medulla
We discussed the adrenal medulla in Chapter 14 as part oF the
autonomic nervous system, so our coverage here is brieF. ²e
spherical
medullary chromaffin cells
(kro
9
mah-fin), which
crowd around blood-filled capillaries and sinusoids, are modi-
fied postganglionic sympathetic neurons that synthesize the
catecholamines
epinephrine
and
norepinephrine (NE)
via
a molecular sequence From tyrosine to dopamine to NE to
epinephrine.
include a swollen “moon” Face, redistribution oF Fat to the abdo-
men and the posterior neck (causing a “buffalo hump”), easy
bruising, and poor wound healing. Because oF enhanced anti-
inflammatory effects, inFections may become overwhelmingly
severe beFore producing recognizable symptoms. Eventually,
muscles weaken and spontaneous Fractures Force the person to
become bedridden. ²e only treatment is to remove the cause—
be it surgically removing the tumor or discontinuing the drug.
Addison’s disease
, the major hyposecretory disorder oF the
adrenal cortex, usually involves deficits in both glucocorticoids
and mineralocorticoids. Its victims tend to lose weight; plasma
glucose and sodium levels drop, and potassium levels rise. Se-
vere dehydration and hypotension are common. Corticosteroid
replacement therapy is the usual treatment.
Gonadocorticoids (Adrenal Sex Hormones)
Most
gonadocorticoids
secreted by the adrenal cortex are weak
androgens
, or male sex hormones, such as
androstenedione
and
dehydroepiandrosterone
(
DHEA
). Most are converted in tissue
cells to more potent male hormones, such as
testosterone
, and
some are converted to estrogens. ²e amount oF gonadocorti-
coids produced by the adrenal cortex is insignificant compared
with the amounts made by the gonads during late puberty and
adulthood.
²e exact role oF the adrenal sex hormones is still in ques-
tion, but we know that they contribute to axillary and pubic hair
development. In adult women adrenal androgens are thought
to contribute to the sex drive, and they largely account For the
(a) Patient before onset.
(b) Same patient with Cushing’s
syndrome.
The white arrow shows the
characteristic “buffalo hump” of fat on the
upper back.
Figure 16.16
The effects of excess glucocorticoid.
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