Download 1 1 Glucocorticoids Function The main functions of glucocorticoids

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Glucocorticoids Function
The main functions of glucocorticoids (mainly cortisol) are the
following:
I-Carbohydrate metabolism... Increase blood glucose by:1) - Stimulate gluconeogenesis so called glucocorticoid, this
occur by the following mechanism:
A- Induction of the enzymes that control the irreversible reactions
of gluconeogenesis which are
pyruvate carboxylase,
Phosphoenolpyruvate carboxykinase, fructose 1,6-bisphosphatase
& glucose-6-phosphatase.
B-Stimulation of amino acid degradation in peripheral tissues as
muscle so provide substrate of gluconeogenesis.
2)-Reduce peripheral utilization of glucose by extrahepatic tissues.
II-Lipid metabolism… affect lipid metabolism as follow:1)-Lipogenic effect on certain places specially the face & trunk.
2)-Lipolytis effect on certain places as extremities, the exact
cause of this different function on lipid metabolism is not yet
known.
3)-Elevate FFA (Free Fatty Acid) in blood circulation due to:A-Lipolytic effect of glucocorticoids leads to release of FFA.
B-Glucocorticoid reduce peripheral utilization of glucose by
extrahepatic tissues lead to reduction of glycerol formation from
glucose by these tissues , therefore, esterification of fatty acid will
be incomplete lead to release of FFA to the blood circulation.
III-Protein metabolism… affect protein metabolism as follow:1)-Anabolic effect on protein metabolism in the liver.
2)-Catabolic effect on protein metabolism in the extrahepatic
tissues specially muscle, bone, skin & adipose tissues.
IV-Immune system… glucocorticoids reduce immunity as well
as have antiinflammatory effect; this is especially evident when
glucocorticoids are present in a high level.
V-Share in the metabolic response toward trauma.
VI-Minor mineralocorticoid activity.
Mineralocorticoids Function
The main function of mineralocorticoids (mainly aldosterone) is
that it affects sodium-potassium & sodium-hydrogen ion
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exchange across all cell membranes.
Transport of Adrenal Steroid Hormones
These hormones are synthesized in the final form & secreted
immediately into the blood circulation.
In the blood circulation:**Cortisol is present in two forms:1- Unbound (free) cortisol constitutes about 8% of the total
plasma cortisol & represents the biologically active fraction.
2- Bound cortisol represents the biologically inactive & reservoir
fraction, the proteins that bind to cortisol are of two forms which
are:A- Corticosteroid-binding globulin (CBG) produced in the liver,
&its synthesis is increased by estrogens. CBG binds 79% of the
total plasma cortisol level; Binding to CBG is not restricted to
cortisol but deoxycorticosterone & progesterone can bind to it.
B-Albumin binds 13% of the total plasma cortisol level.
**Aldosterone: the bound form not has a specific plasma
transport protein but is carry in blood circulation weakly bound
to albumin.
Metabolism of Adrenal Steroid Hormones
Metabolism occurs in the liver through two steps which are:Step 1:- Reduction of A-Ring of cortisol or aldosterone forming
Dihydro or Tetra-hydro cortisol or aldosterone respectively.
Step 2:- Conjugation of Dihydro or Tetra-hydro cortisol (or
aldosterone) at position 3 by glucuronate or sulphate forming
Dihydro or Tetra-hydro cortisol (or aldosterone) 3-glucuronate or
sulphate respectively, these metabolites are water soluble, therefore,
they are excreted through the bile duct where majority of them are
reabsorbed by enterohepatic circulation making 70% of these
metabolites are excreted by urine while 20% are excreted by feces &
10% through the skin.
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