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• Adrenal Glands


  • Lie at the superior poles of the two kidneys
  • Each gland is composed two major parts
• Adrenal medulla


  • Related to the sympathetic nervous system
  • Secretes epinephrine and norepinephrine
• Adrenal cortex


  • Secretes corticosteroids
  • Synthesized from the steroid cholesterol
• Corticosteroids


  • Mineralcorticoids
  • Glucocorticoids
  • Androgens
• Mineralocorticoids


  • Affect electrolytes of the ECF, especially sodium and potassium
  • Principal mineralocorticoid is aldosterone
• Glucocorticoids


  • Increase blood glucose concentration
  • Effects on protein and fat metabolism, carbohydrate metabolism
  • Principal glucocorticoid is cortisol
• Synthesis and secretion of adrenocortical hormones

  1. Zona glomerulosa

  2. Zona fasciculata

  3. Zona reticularis
• Adrenocortical Hormones are Steroids Derived From Cholesterol
• Adrenocortical Hormones are Bound to Plasma Proteins
• Adrenocortical Hormones are Metabolized in the Liver
• Mineralocorticoid Deficiency


  Causes severe renal sodium chloride wasting and hyperkalemia
• Aldosterone


  • The major mineralocorticoid secreted by the adrenals
  • Has greater mineralocorticoid activity than cortisol
• 11ẞ-hydroxysteroid dehydrogenase type 2 prevents cortisol from activating mineral corticoid receptors by converting cortisol to cortisone
• Apparent mineralocorticoid excess syndrome (AME)

  • Deficiency of 118-H502 activity
  • Low aldosterone levels
• Aldosterone


  Increases renal tubular reabsorption of sodium and secretion of potassium
• Excess Aldosterone


  Increases extracellular fluid volume and arterial pressure but has only a small effect on plasma sodium concentration
• Aldosterone deficiency


  Causes hyponatremia
• Pressure natriuresis and pressure diuresis

  Rise in arterial pressure and increase kidney excretion of sodium and water
• Aldosterone escape


  Return to normal sodium and water excretion by the kidneys as a result of natriuresis and diuresis
• Circulatory shock


  Severe ECF fluid dehydration and low blood volume
• Excess Aldosterone


  Causes hypokalemia and muscle weakness
• Aldosterone deficiency


  Causes hyperkalemia and cardiac toxicity
• Excess Aldosterone


  Increases tubular hydrogen ion secretion and causes alkalosis
• Aldosterone


  Stimulates sodium and potassium transport in sweat glands, salivary glands, and intestinal epithelial cells
• Cellular mechanism of aldosterone action

  1. Aldosterone diffuses to the interior of the tubular epithelial cells

  2. Aldosterone combines with mineralocorticoid receptor protein in the cytoplasm

  3. Aldosterone-receptor complex diffuses into the nucleus

  4. Induces formation of mRNA related to sodium and potassium transport

  5. mRNA causes protein formation including sodium potassium ATPase
• Possible nongenomic actions of aldosterone and other steroid hormones

  Increase formation of CAMP in vascular smooth muscle cells and epithelial cells of the renal collecting tubules
• Regulation of aldosterone secretion


  1. Increase potassium concentration in ECF increases aldosterone secretion

  2. Increase angiotensin II concentration in ECF increases aldosterone secretion

  3. Increase sodium ion concentration in ECF decreases aldosterone secretion

  4. Increase atrial natriuretic peptide decreases aldosterone secretion

  5. ACTH from anterior pituitary is necessary for aldosterone secretion
• Potassium ion concentration and angiotensin II are the most potent in regulating aldosterone secretion
• Effects of cortisol on carbohydrate metabolism

  • Stimulation of gluconeogenesis by the liver
  • Cortisol antagonizes insulin's effects to inhibit gluconeogenesis
  • Decreased glucose utilization by cells
  • Elevated blood glucose concentration and "adrenal diabetes"
• 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
• Effects of cortisol on fat metabolism

  • Mobilization of fatty acids
  • Excess cortisol causes obesity
• Cortisol is important in resisting stress and inflammation


  • Stress causes increase in ACTH secretion and adrenocortical secretion of cortisol
  • Anti-inflammatory effects of high levels of cortisol
• Regulation of cortisol by adrenocorticotropic hormone from the pituitary gland

  1. ACTH stimulates cortisol secretion

  2. ACTH secretion is controlled by corticotropin releasing factor from the hypothalamus

  3. ACTH activates adrenocortical cells to produce steroids by increasing CAMP

  4. Physiological stress increases ACTH and adrenocortical secretion

  5. Inhibitory effect of cortisol on the hypothalamus and anterior pituitary to decrease ACTH secretion
• Synthesis and secretion of ACTH in association with melanocyte-stimulating hormone, lipotropin and endorphin