Most hypertension is essential, but a meaningful minority has an endocrine cause. Primary aldosteronism and Cushing's syndrome are the two that appear most often in the Endocrinology and Diabetes SCE and in MRCP, and both are thought to be under-recognised in everyday practice.

When an endocrine cause is considered

  • Hypertension in a young patient, or hypertension that remains difficult to control.
  • Low potassium, although many patients with primary aldosteronism have a normal potassium.
  • An adrenal nodule found incidentally on imaging.
  • Clinical features of cortisol excess, such as easy bruising, proximal muscle weakness, wide purple striae, and new diabetes or osteoporosis.

Primary aldosteronism

Primary aldosteronism is autonomous aldosterone production by the adrenal glands, either from a single adenoma or from bilateral adrenal hyperplasia. The usual screening test is the aldosterone to renin ratio. Exams often focus on interpretation: many medicines and a low potassium can affect the result, so the drug history matters. A raised ratio is followed by confirmatory testing and imaging, and specialist tests are used to decide whether one or both adrenal glands are responsible.

Cushing's syndrome

Cushing's syndrome is the clinical picture produced by prolonged exposure to excess glucocorticoid. The commonest cause overall is prescribed steroids, including inhaled, topical and injected preparations, so the medication history comes first. Endogenous causes are divided into ACTH-dependent disease, mainly pituitary Cushing's disease and ectopic ACTH production, and ACTH-independent adrenal disease.

The recognised screening tests are the overnight dexamethasone suppression test, late-night salivary cortisol and 24-hour urinary free cortisol. Oestrogen-containing medicines and states such as alcohol excess, severe depression and obesity can produce misleading results.

What examiners test

Questions in this area usually reward careful reading rather than rare facts: a patient on a medicine that alters the aldosterone to renin ratio, a woman on the combined pill with an abnormal suppression test, or an incidental adrenal mass that needs functional assessment.

How to revise

Learn the mechanism behind each test, because that explains every source of interference. Then practise questions that give you numbers and a drug list together.