Adrenal cortex

• Adrenal glands are called the life saving glands or essential glands because absence of adrenocortical hormone causes death within week
• Adrenal cortex develops from mesonephrons.
• Adrenal cortex is formed by 3 layers:

  1. Outer zona glomerulosa - secretes mineralocorticoids
  2. Middle zona fasciculata - secretes glucocorticoids & small quantity of sex hormones
  3. Inner zona reticularis - secretes sex hormones & small quantity of glucocorticoids
• All adrenocortical hormones are steroid and synthesized mainly from cholesterol
• Small quantity of cholesterol is also synthesized in cortical cell from acetyl - CoA
• Mineralocorticoids

  Hormones transported in blood by binding with plasma proteins, especially globulins. 50% are present in free form.
• Glucocorticoids

  Hormones transported by a special plasma protein known as glucocorticoids-binding globulin or transcortin. 94% are transported by this protein, 6% are found in free form.
• Adrenal sex hormones transported by sex hormone-binding globulin
• Fate of corticosteroids

  1. Degraded mainly in the liver

  2. Conjugated to form glucuronides

  3. Conjugated to form sulfates

  4. 25% excreted in bile and feces

  5. 75% excreted in urine
• Mineralocorticoids

  Corticosteroids that act on the minerals (electrolytes), particularly sodium and potassium
• Mineralocorticoids

  • Aldosterone
  • 11-deoxycorticosterone
• aldosterone has 3 important functions:

  1. reabsorption of sodium from renal tubules
  2. excretion of potassium through renal tubules
  3. secretion of hydrogen into renal tubules
• Along with sodium ions, simultaneously water is also reabsorbed which leads to increase in ECF volume which leads to increase in blood pressure
• Aldosterone induced high blood pressure decreases ECF through:

  1. Atrial natriuretic peptide from atrial muscles causes excretion of sodium
  2. Caused pressure diuresis that decreases salt and water content in ECF
• Mode of action :

  1. Aldosterone is lipid soluble, diffuses readily into cytoplasm of Tubular epithelial cells through lipid layer of cell membrane
  2. In cytoplasm, binds with special receptor protein
  3. This complex diffuses into nucleus where it binds with DNA and causes formation of mRNA
  4. mRNA diffuses back into cytoplasm, causing protein synthesis like sodium-potassium ATPase
• Aldosterone secretion: 4 imp factors

  1. Increase in potassium ion (K+) concentration in ECF

  2. Decrease in sodium ion (Na+) concentration in ECF

  3. Decrease in ECF volume

  4. Adrenocorticotropic hormone (ACTH)
• Renin-angiotensin mechanism

  1. Renin secreted from juxtaglomerular apparatus of kidney acts on angiotensinogen in the plasma and converts it into angiotensin I

  2. Angiotensin I is converted into angiotensin II by converting enzyme (ACE) secreted by lungs

  3. Angiotensin II acts on the zona glomerulosa to secrete aldosterone

  4. Aldosterone increases the reabsorption of sodium and water, and excretion of potassium

  5. Increased sodium ion concentration and ECF volume inhibit the juxtaglomerular apparatus and stop the release of renin
• Adrenocorticotropic hormone (ACTH)

  Mainly stimulates the secretion of glucocorticoids, has only a mild stimulatory effect on aldosterone secretion
• Glucocorticoids are :

  1. Cortisol
  2. Corticosterone
  3. Cortisone
• Cortisol


  Life protecting hormone
• Functions of glucocorticoids

  1. On carbohydrate metabolism
  2. On protein metabolism
  3. On fat metabolism
  4. On water metabolism
  5. On mineral metabolism
  6. On bone
  7. On muscle
  8. On blood cells
  9. On vascular response
  10. On CNS
  11. permissive actions
  12. On resistance to stress
  13. Anti-inflammatory effects
  14. Anti allergic actions
  15. Immunosuppressive effects
• On carbohydrate metabolism

  1. By promoting gluconeogenesis in liver from amino acids : Enhance breakdown of proteins in extra hepatic cells, releasing amino acids in circulation.
  2. By inhibiting the uptake and utilisation of glucose by peripheral cells (anti-insulin)
• On protein metabolism:

  Catabolism of protein:

  1. Decrease in cellular protein
  2. Increase in plasma level of amino acids
  3. Increase in protein content in liver.
• On protein metabolism

  Catabolism of protein by method:

  1. Releasing amino acids from body cells except liver cells
  2. Increase uptake of amino acids by hepatic cells
• On fat metabolism: ketogenic effect of glucocorticoids 


  Actions on fat:

  1. Mobilization of fatty acids from adipose tissue
  2. Increasing concentration of fatty acids in blood
  3. Increasing utilisation of fat for energy
• On water metabolism:

  Acceleration of excretion of water
• On mineral metabolism:

  Enhance retention of sodium and to lesser extent increase excretion of potassium
• On bone:

  Stimulate osteoclastic activity (bone resorption) and inhibit osteoblastic activity (bone formation and mineralization)
• On muscles

  Increase catabolism of proteins
• On Blood cells

  Decrease number of circulating eosinophils by increasing destruction of eosinophils in reticuloendothelial cells. They also decrease basophils and lymphocytes and increase neutrophils, RBCs and plateletes
• On vascular response

  Presence of glucocorticoids is essential for constriction action of adrenaline & nor adrenaline
• On CNS

  Insufficiency causes personality changes like irritability and lack of concentration

  Sensitivity to olfactory and taste stimuli increases in adrenal insufficiency
• Permissive actions

  Execution of action of some hormones only in presence of glucocorticoids:

  1. Calorigenic effect of glucagon
  2. Lipolytic effect of catecholamines
  3. Vascular effect of catecholamines
  4. Bronchodilator effect of catecholamines
• On resistance to stress

  Glucocorticoids enhance the resistance by:

  1. Immediate release and transport of amino acids from tissues to liver cells to form new proteins essential to withstand stress
  2. Release of fatty acids from cells for production of more energy during stress
  3. Enhancement of vascular response to catecholamines and fatty acid mobilizing action necessary to withstand stress
  4. Prevention of severity of other changes in body by stress