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 exchange across all cell membranes.
Transport of Adrenal Steroid Hormones
These hormones are synthesized in the final form & se creted 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) pro duced 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 spe cific 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.