Adrenocortical Hormones

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Adrenocortical Hormones Dr. Meg-angela Christi Amores

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Adrenocortical Hormones. Dr. Meg- angela Christi Amores. Adrenal Glands. Functional anatomy: Normal weight: 4 grams Located on the superior poles of the kidneys 2 parts: adrenal medulla adrenal cortex. Adrenal Glands. adrenal medulla the central 20 per cent of the gland - PowerPoint PPT Presentation

Transcript of Adrenocortical Hormones

Page 1: Adrenocortical  Hormones

Adrenocortical Hormones

Dr. Meg-angela Christi Amores

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Adrenal Glands

• Functional anatomy:– Normal weight: 4 grams– Located on the superior

poles of the kidneys– 2 parts: – adrenal medulla – adrenal cortex

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Adrenal Glands

• adrenal medulla• the central 20 per cent of the gland• functionally related to the sympathetic nervous system• secretes the hormones epinephrine and norepinephrine

• adrenal cortex • Secretes corticosteroids• all synthesized from the steroid cholesterol

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Adrenocortical hormones

• mineralocorticoids • they especially affect the electrolytes (the "minerals")

of the extracellular fluids-sodium and potassium• Aldosterone is the principal mineralocorticoid

• Glucocorticoids• they exhibit important effects that increase blood

glucose concentration• cortisol is the principal glucocorticoid.

• androgenic hormones

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Adrenal Cortex

• 3 layers:1. Zona glomerulosa

– Secrete aldosterone

2. Zona fasciculata– Secretes cortisol and

corticosterone, androgens, estrogen

3. Zona reticularis– secretes the adrenal androgens

dehydroepiandrosterone (DHEA) and androstenedione

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Adrenocortical hormones

• All human steroid hormones, including those produced by the adrenal cortex, are synthesized from cholesterol

• Cholesterol is provided by low-density lipoproteins (LDL) in the circulating plasma

• Transport of cholesterol is regulated by feedback mechanisms

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Adrenocortical hormones

• Mineralocorticoids– Aldosterone (very potent, accounts for about 90 per cent of

all mineralocorticoid activity) – Desoxycorticosterone (1/30 as potent as aldosterone, but

very small quantities secreted) – Corticosterone (slight mineralocorticoid activity) – 9α-Fluorocortisol (synthetic, slightly more potent than

aldosterone) – Cortisol (very slight mineralocorticoid activity, but large

quantity secreted) – Cortisone (synthetic, slight mineralocorticoid activity)

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Adrenocortical hormones

• Glucocorticoids– Cortisol (very potent, accounts for about 95 per cent of all

glucocorticoid activity) – Corticosterone (provides about 4 per cent of total

glucocorticoid activity, but much less potent than cortisol) – Cortisone (synthetic, almost as potent as cortisol) – Prednisone (synthetic, four times as potent as cortisol) – Methylprednisone (synthetic, five times as potent as

cortisol) – Dexamethasone (synthetic, 30 times as potent as cortisol)

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Adrenocortical hormones

• Adrenocortical Hormones Are Bound to Plasma Proteins. – 90 to 95% cortisol bound to plasma proteins:

• cortisol-binding globulin or transcortin and, to a lesser extent, to albumin

• slows the elimination of cortisol from the plasma• Long halflife of 60 – 90 minutes

– 60% of aldosterone bound to proteins• aldosterone has a relatively short half-life of about 20 minutes

• Adrenocortical Hormones Are Metabolized in the Liver

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Adrenocortical hormones

• mineralocorticoids • they especially affect the electrolytes (the "minerals")

of the extracellular fluids-sodium and potassium

•Aldosterone is the principal mineralocorticoid

• Glucocorticoids• they exhibit important effects that increase blood

glucose concentration• cortisol is the principal glucocorticoid.

• androgenic hormones

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Aldosterone

• Increases Renal Tubular Reabsorption of Sodium and Secretion of Potassium– net effect of excess aldosterone in the plasma is to

increase the total quantity of sodium in the extracellular fluid while decreasing the potassium

– lack of aldosterone secretion can cause transient loss of 10 to 20 grams of sodium in the urine a day and accumulation of potassium

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Aldosterone

• Excess Aldosterone Causes Hypokalemia and Muscle Weakness

• Excess Aldosterone Increases Tubular Hydrogen Ion Secretion, and Causes Mild Alkalosis

• Too Little Aldosterone Causes Hyperkalemia and Cardiac Toxicity

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Regulation of Aldosterone

• intertwined with the regulation of extracellular fluid electrolyte concentrations, extracellular fluid volume, blood volume, arterial pressure

• almost entirely independent of the regulation of cortisol and androgens

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Aldosterone Regulation• Increased potassium ion concentration in the

extracellular fluid greatly increases aldosterone secretion. • Increased activity of the renin-angiotensin system

(increased levels of angiotensin II) also greatly increases aldosterone secretion.

• Increased sodium ion concentration in the extracellular fluid very slightly decreases aldosterone secretion.

• ACTH from the anterior pituitary gland is necessary for aldosterone secretion but has little effect in controlling the rate of secretion

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Adrenocortical hormones

• mineralocorticoids • they especially affect the electrolytes (the "minerals")

of the extracellular fluids-sodium and potassium• Aldosterone is the principal mineralocorticoid

• Glucocorticoids• they exhibit important effects that increase blood

glucose concentration

•cortisol is the principal glucocorticoid.

• androgenic hormones

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Effects of Cortisol on Carbohydrate metabolism

• Stimulation of Gluconeogenesis• Decreased Glucose Utilization by Cells• Elevated Blood Glucose Concentration and

"Adrenal Diabetes."

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Effects of Cortisol on Carbohydrate metabolism

• Stimulate gluconeogenesis*• *formation of carbohydrate from proteins and some

other substances• Best-known metabolic effect of cortisol1. Cortisol increases the enzymes required to convert

amino acids into glucose in the liver cells2. Cortisol causes mobilization of amino acids from the

extrahepatic tissues mainly from muscle.

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Effects of Cortisol on Protein Metabolism

• Reduction in Cellular Protein• Cortisol Increases Liver and Plasma Proteins• Increased Blood Amino Acids, Diminished

Transport of Amino Acids into Extrahepatic Cells, and Enhanced Transport into Hepatic Cells

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Effects of cortisol on Fat Metabolism

• Mobilization of Fatty Acids• increases the concentration of free fatty acids in the

plasma• helps shift the metabolic systems of the cells from

utilization of glucose for energy

• Obesity Caused by Excess Cortisol - buffalo-like torso and a rounded "moon face”– excess deposition of fat in the chest and head

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Other effects of cortisol

• Important in resisting stress and inflammation

• Blocks the Inflammatory Response to Allergic Reactions

• Effect on Blood Cells and on Immunity in Infectious Diseases

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Regulation

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Abnormalities of Adrenocorical Secretion

• Addison’s disease (hypoadrenalism)– failure of the adrenal cortices to produce

adrenocortical hormones– Mineralocorticoid, Glucocorticoid deficiency– Melanin pigmentation

• Cushing’s syndrome (hyperadrenalism)– Hypersecretion by the adrenal cortex causes a

complex cascade of hormone effects– Mostly an excess of cortisol secretion

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