Why it matters in the exam
Adrenal insufficiency appears regularly in the Endocrinology and Diabetes SCE because it combines diagnostic reasoning with urgent, life-saving management. Questions test whether you can recognise the condition, interpret the investigations correctly and act quickly when a patient becomes unwell.
Primary or secondary?
Primary adrenal insufficiency, usually autoimmune Addison's disease in the UK, causes deficiency of both cortisol and aldosterone. ACTH is high, which can cause skin and buccal pigmentation, and mineralocorticoid deficiency causes hyponatraemia, hyperkalaemia and postural hypotension. Secondary adrenal insufficiency results from pituitary or hypothalamic disease, or most commonly from suppression by long-term glucocorticoid therapy. ACTH is low or inappropriately normal, there is no pigmentation, and aldosterone production is preserved, so hyperkalaemia is not expected.
In exam stems, look for clues such as other autoimmune conditions, recent withdrawal of steroids, a history of pituitary surgery or radiotherapy, or treatment with high-dose inhaled or injected corticosteroids.
Investigations
A morning serum cortisol is a useful first test, and a short Synacthen test confirms the diagnosis when the result is equivocal. Interpret cortisol results against the cut-off for the local assay, because newer immunoassays give lower values than older methods. Measure ACTH alongside cortisol to separate primary from secondary disease. In primary disease, check adrenal autoantibodies and consider imaging or other causes if antibodies are negative. Remember that recent glucocorticoid use, including some inhaled preparations, affects the results.
Adrenal crisis
Adrenal crisis is a medical emergency. Typical features are vomiting, abdominal pain, confusion, hypotension and shock, often triggered by infection, surgery or missed doses. Do not delay treatment to confirm the diagnosis. Give hydrocortisone 100 mg intravenously or intramuscularly immediately, followed by continuing parenteral hydrocortisone, and start intravenous fluid resuscitation with careful monitoring of sodium and glucose. Take blood for cortisol and ACTH before the first dose if this does not delay treatment.
Long-term management and sick day rules
Patients are usually treated with hydrocortisone in divided daily doses, and those with primary disease also need fludrocortisone. Education is central. Patients should double their usual glucocorticoid dose during intercurrent illness with fever, use injectable hydrocortisone if they are vomiting, and carry a Steroid Emergency Card. In the UK, patients on long-term steroids at risk of adrenal suppression should also be identified and given emergency advice, a point that features in safety-focused exam questions.
Exam tips
If a stem describes a patient on long-term steroids who is unwell after surgery or infection, think of adrenal crisis first. If potassium is high and the patient is pigmented, think primary disease. When asked for the immediate next step in an unstable patient, the answer is almost always hydrocortisone and fluids rather than another test.
Practise with License Medical
The License Medical Endocrinology and Diabetes question bank includes exam-style Best of Five questions on this topic and across the curriculum, each with a guideline-based explanation. Start revising at license-medical.com/question-bank-details/endocrinology-and-diabetes/.
Sources: Society for Endocrinology guidance on adrenal crisis; National Patient Safety Alert on steroid emergency cards (2020).