Page 309 - Color_Atlas_of_Physiology_5th_Ed._-_A._Despopoulos_2003

Adrenal Cortex and Glucocorticoid called steroid diabetes in extreme cases. Thus,
Synthesis cortisol has a catabolic effect (degrades pro-
teins) that results in the increased excretion of
The mineralocortico(stero)ids aldosterone, urea.
corticosterone and 11-desoxycorticosterone Cardiovascular function: Glucocorticoids
(! pp. 182ff. and 294) are synthesized in the increase myocardial contractility and vasocon-
glomerular zone of the adrenal cortex (! A1), striction due to enhancement of cate-
whereas the glucocortico(stero)ids cortisol cholamine effects (! pp. 194 and 214). These
(hydrocortisone) and cortisone (! p. 294, are described as permissive effects of cortisol.
small quantities) are synthesized in the fascic- Cortisol increases the synthesis of epinephrine
Hormones and Reproduction sulfated form, DHEA-S) to synthesize various doses, glucocorticoids induce anti-inflam-
in the adrenal medulla (! A6) and of angioten-
ular zone (! A2). Androgens are synthesized
sinogen in the liver (! p. 184).
in the reticular zone of the adrenal cortex (!
Especially when administered at high
A3). One of the androgens is dehydroepian-
drosterone (DHEA), which is used (partly in its
matory and anti-allergic effects because they
sex hormones in other tissues (! p. 304).
stabilize lymphokine synthesis and histamine
Cortisol transport. Most of the plasma corti-
release (! p. 100). On the other hand, inter-
leukin-1, interleukin-2 and TNF-α (e.g., in
sol is bound to transcortin, or cortisol-binding
globulin (CBG), a specific transport protein
severe infection) leads to increased secretion
with a high-affinity binding site for cortisol.
Renal function: Glucocorticoids delay the excretion
mational changes of CBG due to inflammation
of water and help to maintain a normal glomerular fil-
11 Cortisol is released in response to confor- of CRH and high cortisol conc. (see below).
etc.
tration rate. They can react also with aldosterone re-
CRH and ACTH regulate cortisol synthesis ceptors but are converted to cortisone by 11!-hy-
and secretion (! A4, A5; see also p. 270). ACTH droxysteroid oxidoreductase in aldosterone target
ensures also structural preservation of the cells. Normal cortisol conc. are therefore ineffective
adrenal cortex and supplies cortisol precur- at the aldosterone receptor. High conc., however,
sors, e.g., by forming cholesterol from its have the same effect as aldosterone (! p. 182).
Gastric function: Glucocorticoids weaken the
esters, by de novo synthesis of cholesterol and protective mechanisms of the gastric mucosa. Thus,
by converting it to progesterone and 17α-hy- high-dose glucocorticoids or stress (see below) in-
droxyprogesterone (! pp. 256 and 294). ACTH crease the risk of gastric ulcers (! p. 242).
secretion is stimulated by CRH and epineph- Cerebral function: High glucocorticoid conc.
rine and inhibited (negative feedback control) change hypothalamic (! A) and electrical brain ac-
by cortisol with or without the aid of CRH (! A; tivity (EEG) and lead to psychic abnormalities.
see also p. 273 A). Stress: Physical or mental stress increases cor-
A circadian rhythm of CRH secretion and thus of tisol secretion as a result of increased CRH
ACTH and cortisol secretion can be observed. The secretion and increased sympathetic tone
peak secretion is in the morning (! B, mean values). (! A). Many of the aforementioned effects of
Continuous hormone conc. sampling at short inter- cortisol therefore play a role in the body’s re-
vals have shown that ACTH and cortisol are secreted sponse to stress (activation of energy metabo-
in 2–3-hour episodes (! B).
lism, increase in cardiac performance, etc.). In
Receptor proteins (! p. 278) for glucocorti- severe physical (e.g., sepsis) or mental stress
coids can be found in virtually every cell. Glu- (e.g., depression), the cortisol plasma conc. re-
cocorticoids are vital hormones that exert mains at a very high level (up to 10 times the
numerous effects, the most important of normal value) throughout the day.
which are listed below.
Carbohydrate and amino acid (AA) metabo-
lism (see also pp. 283 A and 285 C): Cortisol
uses AA derived from protein degradation to
296 increase the plasma glucose concentration
(gluconeogenesis), which can lead to the so-
Despopoulos, Color Atlas of Physiology © 2003 Thieme
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