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ANATOMY & PHYSIOLOGY OF ADRENAL GLAND

• The adrenal gland is made up of cortex and medulla producing steroid hormone and catecholamine respectively.

• The adrenal cortex produces three types of steroids

  • Glucocroticoids : Cortisol

  • Mineralocorticoids : Aldosterone

  • Gonadocorticoids : Testosterone and estrogen.

• Glucocorticoids are produced from zona glomerulosa, whereas the latter two groups are produced from zona fasiculata and reticularis.

Cortisol

• Cortisol is secreted from the cortex of the adrenal gland in response to direct stimulation by ACTH.

• ACTH secretion is stimulated by the hormone corticotropin releasing factor released from the hypothalamus. This occurs in a diurnal rhythm with higher levels secreted in the morning and lower levels in the evening.

• Plasma cortisol suppresses the release of ACTH by negative feed back mechanism.

• Functions of cortisol includes :

  • They facilitate the patient response to stress response affecting the heart, vasular bed, water excretion, electrolyte balance, potentiation of catecholamine action and control of water distribution.

  • It affects protein, fat and carbohydrate metabolism by producing glucose by glycogenolysis and neoglycogenesis

  • It promotes growth and development but, in excess interfere with GI tarct mucosa and leading to peptic ulcer.

Aldosterone

• It is controlled by RAAS and serum potassium concentration.

• The RAAS controls aldosterone levels in changes in volume, posture and sodium intake.

• It regulates extracellular volume and controls the sodium and volume balance. They maintain sodium and potassium plasma concentration.

Gonadocorticoids : They responsible for sexual functions.

ADRENAL CRISIS

• The adrenal gland synthesis steroid hormone in the cortex and catecholamines in the medulla.

• Adrenal insufficiency refers to a state of deficiency of a adrenal gland hormone production in the cortex.

• Adrenal crisis is a life threatening exacerbation of adrenal insufficiency due to increased physiological demand or decreased supply of cortisol.

• Adrenal crisis usually occurs in response to major stress, such as MI, sepsis, surgery, major injury, trauma or other illness. The most frequent iatrogenic cause for acute adrenal crisis is rapid withdrawal of steroids in patients with adrenal atrophy secondary to long term steroid administration. About 20% of patients with AIDS will eventually develop adrenal insufficiency.

Etiology

• Primary Adrenal Insufficiency or Addison's disease

  • It is due to intrinsic adrenal gland dysfunction resulting in cortisol and aldosterone production.

  • Approx 90% of the gland must be destroyed for clinical adrenal insufficiency.

• Secondary Adrenal Insufficiency is due to hypothalmic pituitary dysfunction causing inadequate ACTH production. This results in cortisol deficiency only. This may be caused by withdrawal of prolonged steroid therapy, pituitary disease, head trauma or post partum pituitary necrosis (Sheehan Syndrome).

Clinical Features

Investigations

• Random cortisol :

  • It is usually low in adrenal insufficiency , but may be within normal range but inappropriately low for serious ill patient.

  • Hence cannot be used to confirm the diagnosis.

  • A serum cortisol >18mg/dl rules out adrenal insufficency.

• ACTH stimulation test or short synacthen test can be done to differentiate between primary and secondary adrenal insufficiency.

• Plasma sodium and potassium levels

• Plasma renin activity and aldosterone levels

Treatment

• ABC

• Fluid resuscitation with 5% Dextrose in normal saline in fluid of choice to correct both hypoglycemia and hyponatremia.

• Steroids

  • Hydrocortisone 100mg IV bolus is the drug of choice for adrenal insufficiency.

Or

• Dexamethasone 4mg IV bolus

• Vasopressor

  • Administrated if unresponsive to fluid and steroid therapy.

• Supplementation

  • Patient may require life long supplementation of glucocortiocds with or without mineralocorticoids.

Note

• Patients with chronic adrenal insufficiency in normal circumstance requires 20 – 30mg/day.

• During minor stress : 25 mg/day of hydrocortisone is supplemented for 1- 3 days.

• During major stress : 50 - 75 mg/day of hydrocortisone is supplemented 1- 3 days .

• During severe stress : 100 - 150 mg/day of hydrocortisone is supplemented 1- 3 days.

Updated on 17/3/2014

Reference

• Davidson

• Tintinalli