Addison's disease (E&M) Flashcards
What is Addison’s disease?
Primary adrenal insufficiency - destruction of adrenal cortex –> decreased production of adrenocortical hormones - glucocorticoids (cortisol) and mineralocorticoids (aldosterone)
What are the main steroids that are deficient in Addison’s disease? (3)
- cortisol
- aldosterone
- dehydroepiandrosterone (DHEA) + sulfated conjugate (DHEA-S)
What is Addison’s disease the commonest cause of?
Adrenocortical failure in the UK
What are the main causes of Addison’s disease? (3+3)
- autoimmune (more developed countries)
- tuberculosis (more common worldwide)
- metastases
- (meningococcal septicaemia –> Waterhouse-Friderichsen syndrome)
- (HIV)
- (antiphospholipid syndrome)
What are some risk factors for Addison’s disease? (8)
- female sex
- adrenocortical antibodies
- adrenal haemorrhage
- autoimmune diseases
- coeliac disease
- TB/non-TB infection
- sarcoidosis
- anticoagulant use
What is an Addisonian crisis?
A sudden worsening of symptoms and drop in cortisol levels, caused by:
- sudden withdrawal of steroids if patient on long-term steroids
- sepsis
- surgery
What are the clinical features of Addison’s disease? (7)
- fatigue
- anorexia
- weight loss
- hyperpigmentation (low cortisol = increased ACTH –> increased POMC –> increased a-MSH)
- nausea, vomiting, abdominal pain
- postural hypotension
- hypoglycaemia –> dizziness
What might you see on examination in Addison’s disease? (2)
- hyperpigmentation - exaggerated over pressure points on elbows, area of buccal hyperpigmentation where teeth pinch mucous membrane while chewing
- hypotension (can be postural)
Why does hyperpigmentation occur in Addison’s disease?
Low cortisol –> negative feedback increases ACTH –> increased POMC –> increased alpha-MSH
What are the features of an Addisonian crisis? (2)
Severe hypovolaemia and hyponatraemia
What are the first-line investigations for Addison’s disease?
- ACTH stimulation test (short synACTHen test)
- morning serum cortisol
- plasma ACTH
- serum electrolytes
- U&Es
What is the definite investigation done in Addison’s disease?
ACTH stimulation test (short synACTHen test):
- plasma cortisol measured before and 30min after giving Synacthen 250mg IM
- Synacthen should stimulate cortisol secretion but does not happen in Addison’s disease
- serum cortisol <550nmol/L indicates adrenal failure
When do we do morning serum cortisol for Addison’s disease?
- done if short Synacthen test is unavailable e.g. in primary care
- 9am blood test (cortisol peaks in morning) - if low, suspect Addison’s disease
- > 500nmol/L = very unlikely
- 100-500nmol/L = prompt ACTH stimulation test
- <100nmol/L = definitely abnormal
What electrolyte abnormalities might be seen in Addison’s disease (1/3 undiagnosed patients)? (3)
- hyperkalaemia
- hyponatraemia
- hypoglycaemia
What might we see on ABG in Addison’s disease?
Metabolic acidosis with normal anion gap
Anion gap = (Na + K) - (HCO3 + Cl)
Normal = 8-14mmol/L