Adrenal Gland Steroids

Adrenal Gland Diseases

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  • The adrenal cortex produces 3 steroids:
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  • 1. Glucocorticoids
  • 2. Mineralocorticoids
  • 3. Adrenal androgens

Adrenal Gland

Adrenal Gland Steroids


The function of these steroids are:

  • 1. Glucocorticoids – modulate intermediary me­tabolism and immune responses of the body.
  • 2. Mineralocorticoids – Regulate blood pressure, vascular volume and electrolytes.
  • 3. Adrenal androgens are responsible for second­ary sex characters in females. (In males sexual characteristics are regulated by the gonadal ste­roids viz. testosterone).
  • The most important function of the adrenal gland is secretion of cortisol (hydrocortisone) in response to stress.

Disorders of adrenal gland may be :

  • · Hyperfunction or Cushing’s syndrome
  • · Hypofunction or adrenal insufficiency.
  • The release of adrenal cortical hormones occurs in response to ACTH or adrenocorticotropic hormone re­leased by the anterior pituitary gland. ACTH is re=­leased from anterior pituitary gland in response to corticotropin releasing hormone or CRH, released by the hypothalamus.
  • CRH is inhibited by ACTH levels and ACTH is inhibited by cortisol levels in plasma.
  • There are peak ACTH levels before waking up and low ACTH levels before sleeping.

1. Glucocorticoids

  • The most important glucocorticoid is cortisol.
  • Daily secretion of cortisol is between 15 – 30 mg. The liver is the major organ which inactivates ste­roids.
  • The cortisol is secreted in pulses according to circa­dian rhythm, high just before waking up and low be­fore sleepi ng.
  • ACTH and cortisol levels increase with stress, eating, surgery, fever, hypoglycemia, exercise, emotional trauma.
  • Glucocorticoid administration suppresses ACTH re­lease and ACTH levels in plasma falls.
  • Cortisol levels suppress ACTH release from pituitary and release of CRH as well.
  • Prolonged glucocorticoid therapy results in adrenal atrophy, suppression of ACTH, and suppression of CRH release. If CRH is given to such patients then there is a rise in plasma ACTH.
  • All glucocorticoids have some mineralocorticoid prop­erties. The main action of glucocorticoids is produc­tion of energy via glucose. The glucocorticoids also regulate protein, carbohydrate, lipid and nucleic acid metabolism.
  • Glucocorticoids raise blood sugar levels by opposing the actions of insulin, inhibiting glucose uptake, and promoting glucose synthesis by the liver (gluconeo­genesis). It also causes increase in breakdown of pro­teins and excretion of nitrogen (catabolic action).
  • Glucocorticoids have anti-inflammatory properties due to suppression of cytokines.
  • Elevated glucocorticoid levels in response to stress protect the organism in many ways and prevent hy­potension, shock and death.
  • In patients with adrenal insufficiency glucocorticoid administration can save life.

2. Mineralocorticoids

  • Daily secretion of aldosterone, which is the most im­portant mineralocorticoid is between 50 to 250 IJg.
  • Renin produced in the kidney acts on angiotensinogen to form angiotensin 1.
  • Angiotensin I is converted to angiotensin II by angio­tensin converting enzyme (ACE).
  • Angiotensin II stimulates the Zona glomerulosa of
  • . adrenal cortex to secrete aldosterone.
  • Aldosterone levels in plasma increase sodium reten­tion by the kidneys, causing expansion of extra cellu­lar fluid volume and decreased release of renin. •
  • When normal individuals are given aldosterone it causes sodium retention followed by natriuresis and  within 3 days sodium balance is again maintained. Therefore, edema does not develop.
  • This process is called the escape phenomenon be­cause the renal tubules lose the capability to respond to sodium-retaining action of aldosterone.
  • Aldosterone causes a loss of potassium which goes on increasing without any escape resulting in hypokalaemia.
  • Aldosterone secretion is controlled by renin an­giotensin system (RAS), potassium and ACTH.
  • · Angiotensin II stimulates aldosterone secretion.
  • · Potassium ion stimulates aldosterone secretion.
  • · ACTH stimulates aldosterone secretion.

3. Adrenal androgens

  • The major androgen secreted by adrenal is dehydroepiandrosterone (DHEA), 15 – 30 mg daily.
  • Adrenal androgens have almost no effect in males because in males the sex characteristics are regu­lated by testosterone. In females adrenal androgens are responsible for secondary sex characteristics.

 

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