Addison’s disease

Addison’s disease (=primary adrenal insufficiency) occurs when there is destruction of the adrenal cortex, resulting in reduced production of glucocorticoid, mineralocorticoid and sex steroids.  

Untreated it will result in an Addisonian crisis, characterised by hypotension, tachycardia, hypoglycaemia, high potassium and low sodium, which if not promptly managed will result in death.

The commonest cause of Addison’s disease is now autoimmune destruction of the adrenal gland. This is more common in people with HLA-DR3 and HLA-B8

Other causes of Addison’s disease include:
  • Infection 
    • TB = commonest cause worldwide
    • CMV 
    • Histoplasosis 
  • Amyloidosis 
  • Haemorrhage into adrenals 
    • associated with meningococcal septicaemia (=Waterhouse-Freiderickson syndrome) and pseudomonas auregenosa 
  • Metastasis into adrenals

Presentation is vague and can include: 
  • Abdominal pain
  • Fatigue 
  • Muscle weakness 
  • Vomiting
  • Diarrhoea 
  • Headache 
  • Depression

Signs include: 
  • Postural hypotension
  • Hyperpigmentation (due to raised ACTH and MSH) 
  • Weight loss 

  • Low sodium 
  • High potassium 
  • Hypoglycaemia 
  • Eosinophilia 
  • Lymphocytosis 
  • Acidosis 

Diagnosis is by the short synacthen test. 

  • Oral hydrocortisone - 15-20mg/day
  • Fludrocortisone - 50-200 mcg/day
  • 'Sick day rules'
    • double normal dose of PO hydrocortisone if T>37.5
    • if one vomit, take 20mg hydrocortisone PO
    • if two vomits, pt should use emergency 100mg IM hydrocortisone injection and got to ED
    • after any injury, take 20mg hydrocortisone PO
  • In Addisonian crisis: 
    • IV hydrocortisone  - 100mg QDS
    • IV fluids 
    • Treatment of hypoglycaemia 
    • Treat cause - common causes of crisis include infection, diarrhoea and vomiting

Note that some medications, such as ketoconazole, rifampacin and phenytoin, decrease the level of cortisol and should be used with caution in patients with Addisons.  Diuretics and acetazalomide should be avoided.

In around 50% of cases Addison’s disease is associated with other autoimmune conditions, such as diabetes, thyroid disease and pernicious anaemia. 

Small print gem: The adrenal glands have a large reserve and over 90% have to be destroyed before Addison’s disease will develop. 

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