Differentials
Essential hypertension (HTN)
SIGNS / SYMPTOMS
No differentiating signs or symptoms.
INVESTIGATIONS
Aldosterone/renin ratio will be normal if performed off interfering medicines. May be elevated if patient receiving medicines (such as beta-blockers) that cause false positives, in which case test should be repeated after such medicines are withdrawn for at least 2 (and preferably 4) weeks.
A normal ratio in a patient receiving medications that can cause false positives makes primary aldosteronism (PA) highly unlikely.
In a minority of cases of PA, there is unprovoked hypokalaemia.
Thiazide-induced hypokalaemia in patient with essential HTN
SIGNS / SYMPTOMS
History of use of thiazides.
INVESTIGATIONS
Aldosterone/renin ratio will be normal after correcting hypokalaemia and withdrawing thiazide for at least 6 weeks.[72]
Renal artery stenosis
SIGNS / SYMPTOMS
Known renal artery stenosis, history of arterial disease elsewhere, or risk factors for atherosclerosis (e.g., smoking, diabetes mellitus, and hyperlipidaemia).
Liddle syndrome
Syndrome of apparent mineralocorticoid excess
SIGNS / SYMPTOMS
Family history of this syndrome. Hereditary form usually presents in childhood.
History of excessive consumption of liquorice, which can lead to an acquired form.
Hypertensive forms of congenital adrenal hyperplasia
SIGNS / SYMPTOMS
Family history of congenital adrenal hyperplasia due to 11beta-hydroxylase or 17alpha-hydroxylase deficiency.
Usually presents in childhood.
History of either virilisation (in the case of 11beta-hydroxylase deficiency) or feminisation (in the case of 17alpha-hydroxylase deficiency).
INVESTIGATIONS
Although patients are usually hypokalaemic and have suppressed renin levels, aldosterone levels are also low and the aldosterone/renin ratio usually is normal.
In 11beta-hydroxylase deficiency, plasma cortisol and corticosterone are low, whereas basal or adrenocorticotropic hormone-stimulated levels of deoxycorticosterone and 11-deoxycortisol are elevated.
In 17alpha-hydroxylase deficiency, plasma levels of 17alpha-hydroxyprogesterone, 11-deoxycortisol, and cortisol are reduced, whereas gonadotrophins (LH and FSH) are increased.[72][113]
Primary glucocorticoid resistance
SIGNS / SYMPTOMS
Family history of this syndrome (but can be acquired).
May be associated with androgenisation.
INVESTIGATIONS
Although patients are usually hypokalaemic and have suppressed renin levels, aldosterone levels are also low and the aldosterone/renin ratio usually is normal.
Associated with increased adrenocorticotropic hormone and cortisol levels, and resistance of cortisol to adrenal suppression by dexamethasone, in the absence of clinical stigmata of Cushing syndrome.[72][113]
Ectopic adrenocorticotropic hormone syndrome
SIGNS / SYMPTOMS
Clinical findings of underlying tumour.
Clinical findings due to raised cortisol levels (Cushing syndrome) including ecchymoses, muscle weakness, and diabetes mellitus.
INVESTIGATIONS
Although patients are usually hypokalaemic and have suppressed renin levels, aldosterone levels are also low and the aldosterone/renin ratio usually is normal.
Evidence of underlying tumour on imaging studies.
Cortisol and adrenocorticotropic hormone levels elevated and non-suppressible with high-dose dexamethasone.[72][113]
Activating mutations of the mineralocorticoid receptor
Familial hyperkalaemic hypertension (pseudohypoaldosteronism type II, Gordon syndrome)
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