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PHYSIOLOGY OF
ADRENAL GLAND
By
Dr. Mudassar Ali Roomi (MBBS, M.Phil.)
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Zones of adrenal gland
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Zones of adrenal gland
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Hypothalamo-hypophyseal-adrenal axis
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Glucocorticoids
Cortisol (95% of g.c. activity)
Corticosterone (4% of g.c. activity)
Synthetics (potency) Cortisone (1X cortisol)
Prednisone (4X cortisol)
Methylprednisone (5X cortisol)
Dexamethasone (30X cortisol)***
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Plasma proteins binding
Adrenalcortical hormones bind to
Cortisol-binding globulin (transcortin)
Albumin
Bound cortisol 90 to 95% long half life (60 to 90 minutes)
Free aldosterone 40%
short half life (20 minutes)
Bound hormone serves as a reservoirbuffering hormone for use as needed
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Steroid & Thyroid Hormones - Mechanism of Action
Figure 74-6; Guyton & Hall
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Cholesterol- the precursor of steroid hormones
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SYNTHESIS OF
ADRENAL STEROID
HORMONES
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SYNTHESIS OF ADRENAL STEROID HORMONES
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FUNCTIONS OF CORTISOL
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http://www.google.com.pk/url?sa=i&rct=j&q=FUNCTIONS+OF+CORTISOL&source=images&cd=&cad=rja&docid=FH-rHLds8Dv5NM&tbnid=IfeOwRNOHRCgaM:&ved=0CAUQjRw&url=http://faculty.pasadena.edu/dkwon/chapter%207&13%20web%20page/CHapter%207%20and%2013_files/slide0088.htm&ei=FmqtUeCeDoSaO9b3gIgG&bvm=bv.47244034,d.ZWU&psig=AFQjCNFkdEXRGtabiS_GpJQKeqMLTigr0w&ust=1370405765445958 -
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Cortisol
Helps in resisting stress and inflammation
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EFFECTS ON CARBOHYDATRE METABOLISM
Gluconeogenesis
enzymes to convert a.a. glucose
mobilization of a.a. from extrahepatic tissue
Mainly from muscles
glycogen storage in liver
glucose utilization by cells (insulin resistance)
blood glucose (adrenal diabetes)
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EFFECTS ON PROTEIN METABOLISM
Reduces protein stores in almost all cells
decreased protein synthesis
increased catabolism of protein (causes weakness
of muscles) EXCEPT in liver cells
Increases liver & plasma proteins
Increases blood amino acids Decreases transport into extrahepatic cells
Increases transport into hepatic cells
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EFFECTS ON LIPID METABOLISM
Mobilizes fatty acids from adipose cells
Increases oxidation of fatty acids
Helps shift from glucose to fat metabolismduring times of starvation or stress
Conserves body glucose & glycogen
Mobilizes fat from periphery to trunk. Obesity: buffalo torso & round moon face
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Antiinflammatory effects of cortisol
Cortisol has three actions that interfere with the body'sinflammatory response to trauma and irritants. (1) Cortisolinduces the synthesis oflipocortin, an inhibitor of theenzyme phospholipase A2. Phospholipase A2 liberatesarachidonic acid from membrane phospholipids and
provides the precursor for the prostaglandins andleukotrienes that mediate the inflammatory response.Therefore, this component of the antiinflammatory effectof cortisol is based on inhibiting the synthesis of theprecursor to prostaglandins and leukotrienes.
(2) Cortisol inhibits the production ofinterleukin-2 (IL-2)and the proliferation of T lymphocytes.
(3) Cortisol inhibits the release ofhistamine and serotoninfrom mast cells and platelets.
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Anti-inflammatory action of cortisol
http://www.google.com.pk/url?sa=i&rct=j&q=ANTIINFLAMMATORY++CORTISOL&source=images&cd=&cad=rja&docid=SgY4xzrsNIR9qM&tbnid=YSXi_FGjlfJGiM:&ved=0CAUQjRw&url=http://www.people.vcu.edu/~urdesai/adrn.htm&ei=A3OtUdS2J4mZO4mWgPAP&bvm=bv.47244034,d.ZWU&psig=AFQjCNHbjgd4Alo2vHiaiT95uXEnJIthFw&ust=1370408029291205 -
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Suppression of immune response by cortisol
As previously noted, cortisol inhibits theproduction of IL-2 and the proliferation of Tlymphocytes, which also are critical for cellularimmunity.
Exogenous glucocorticoids can be administeredtherapeutically to suppress the immune responseand prevent the rejection of transplanted organs.Also used in allergies and in autoimmune
diseases.
Increased chances of infections
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Maintenance of vascular responsiveness tocatecholamines (permissive role of cortisol)
Cortisol is necessary for the maintenance of
normal blood pressure and plays a permissive rolein the arterioles by up-regulating 1-adrenergicreceptors. In this way, cortisol is required for thevasoconstrictive response of the arterioles to
catecholamines. In hypocortisolism, there is hypotension;
in hypercortisolism, there is hypertension.
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Inhibition of bone formation.
Cortisol inhibits bone formation by:
decreasing the synthesis of type I collagen, the
major component of bone matrix;
by decreasing osteoblast production;
and by decreasing intestinal Ca2+ absorption.
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Increases in glomerular filtration rate (GFR).
Cortisol increases GFR by causing vasodilation
of afferent arterioles, thereby increasing renal
blood flow and GFR.
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Effects on CNS.
Glucocorticoid receptors are found in the brain,
particularly in the limbic system.
Cortisol decreases REM sleep, increases slow-
wave sleep, and increases awake time. (Recall that
the largest bursts of ACTH and cortisol occur just
before awakening at about 8 am.)
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Summary of actions of cortisol
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http://www.google.com.pk/url?sa=i&rct=j&q=UNCTIONS+OF+CORTISOL&source=images&cd=&cad=rja&docid=VNKx43ByYcT1hM&tbnid=AKohmRPJaC9b1M:&ved=0CAUQjRw&url=http://www.genemedics.com/cortisol/&ei=52qtUaCkGYL0OfPdgdAF&bvm=bv.47244034,d.ZWU&psig=AFQjCNExmc2iiy0D9jMB91ijqAYI8gX_XA&ust=1370405760252943