Screening for secondary causes of hypertension is important, though often not thought of.
Primary aldosteronism is the most common endocrine cause. The screening test is the aldosterone-renin ratio (ARR). Primary aldosteronism is likely if
renin < 8.2mU/L
aldosterone >400pmol/L
aldosterone-renin ratio > 50
When should we perform ARR
Severe hypertension, sustained >150/100 on 3 measurements
Resistant hypertension on 3 conventional antiHT incl. diuretics
Controlled hypertension on 4 or more antiHT
Hypertension with hypokalaemia
Adrenal incidentaloma
Sleep apnoea
First degree relative of primary aldosteronism
Family history of early onset hypertension
Family history of young strokes
Tips re checking ARR
Sodium replete
Ambulatory (1-2hr upright or ambulant; mid-morning)
Check electrolytes - K
No interfering drugs
Differential diagnoses include
Bilateral adrenal hyperplasia (idiopathic hyperaldosteronism)
Adrenal adenoma
Unilateral adrenal hyperplasia
Adrenal carcinoma
Familial hyperaldosteronism (Type 1,2,3)
Confirmation tests include
Saline suppression test
Fludrocortisone suppression test
Adrenal CT
Adrenal vein sampling
Author: Andrew To