Dr Soule is a Consultant Endocrinologist and General Medicine Physician at Christchurch Hospital and University of Otago Medical School. He trained at the University of Cape Town, South Africa (many years ago) with further subspeciality training at the Middlesex Hospital and University College London. He enjoys sorting out challenging general medical and endocrinology problems, interacting with medical students and guiding Endocrinology trainees. Research interests have been fairly broad over the years, and have included forays into reproductive endocrinology, adrenal pathology and the vagaries of hyponatraemia.
The Pursuit Of Primary Aldosteronism – Pearls And Pitfalls
Primary aldosteronism (PA) is a group of disorders in which aldosterone production is inappropriately high for sodium status, relatively autonomous of the major regulators of secretion (angiotensin II, plasma potassium), and non-suppressible by sodium loading. Recent studies report PA in 5-10% of hypertensive patients in general and speciality settings, only a minority of whom are hypokalaemic (10-40%). There is clear evidence that patients with PA have higher cardiovascular morbidity and mortality than age-and sex-matched patients with essential hypertension and equivalent BP control. It is reasonable to screen for PA by measuring the plasma aldosterone:renin ratio (ARR) in the following patients – those with early onset hypertension, resistant hypertension (>140/90 on three drugs including a diuretic), those with hypertension and unexplained hypokalaemia and those with hypertension with an adrenal adenoma. The ARR should ideally be measured in untreated hypertensive patients or those on non-interfering drugs (alpha blockers and non-dihydropyridine calcium channel blockers) since virtually all anti-hypertensives can impact on the renin-aldosterone axis. The definitive diagnostic test is the saline suppression test (2L/4hours) with non-suppression of aldosterone confirming autonomous secretion. CT adrenals is of limited value (although universally performed) due to a significant number of false positive and false negative results. Patients with unilateral aldosterone secretion confirmed on adrenal vein sampling are candidates for laparoscopic adrenalectomy which normalises potassium in almost all patients and ‘cures’ hypertension in about 50%. Mineralocorticoid receptor antagonists (spironolactone and eplerenone) are effective at controlling BP and protecting target organs in those with bilateral hyperplasia.