Hypotension, hyponatraemia, hyperkalaemia and hypoglycaemia
Mnemonic
“Sodium down, potassium up, glucose down, pressure down”, the biochemical signature of an adrenal crisis:
- Hyponatraemia, present in most cases
- Hyperkalaemia, only in primary failure, where aldosterone is also lost
- Hypoglycaemia
- Hypotension, refractory to fluids and vasopressors
- Metabolic acidosis, eosinophilia, mild hypercalcaemia
“Primary has pigmentation and potassium; secondary has neither.” Both share the low sodium and low cortisol, but only primary failure loses the mineralocorticoid axis and only primary failure raises ACTH enough to pigment the skin and buccal mucosa.
Treatment precedes confirmation: take a random cortisol and ACTH, then give intravenous hydrocortisone 100 mg and fluids immediately. Waiting for a Synacthen test is a recognised cause of death.
The commonest cause overall is abrupt withdrawal of long term steroids, which is why sick day rules and a steroid card matter, and why the dose is doubled during intercurrent illness.
Expansion
Primary (Addison disease): the adrenal cortex fails, so both cortisol and aldosterone are lost, and ACTH rises.
- Hypotension and postural drop
- Hyponatraemia and hyperkalaemia
- Hypoglycaemia
- Hyperpigmentation, since excess ACTH is cleaved from POMC alongside melanocyte stimulating hormone
- Salt craving, weight loss, fatigue
Secondary (pituitary failure): only cortisol is lost; aldosterone is preserved, since it is driven by the renin-angiotensin system.
- No pigmentation (ACTH is low)
- No hyperkalaemia
- Hyponatraemia may still occur, through loss of cortisol’s inhibition of antidiuretic hormone
Adrenal crisis is precipitated by intercurrent illness, surgery or abrupt withdrawal of steroids, and presents with shock resistant to fluids and vasopressors. Treatment is immediate hydrocortisone with fluids and glucose, before confirmatory tests.
The commonest cause overall is exogenous steroid withdrawal, which suppresses the axis for up to a year.