Apparent Mineralocorticoid Excess (AME) resulting from liquorice ingestion is rare. Liquorice is still popular, however, and must be considered in the differential diagnosis of patients presenting with hypertension and hypokalaemia.
A 62 year-old woman presented with refractory hypertension (blood pressure 200/118 mmHg) and hypokalaemic alkalosis (serum K 2.98 millimoles per litre; bicarbonate 30 millimoles per litre). There was no sign of Cushing's Syndrome. Investigation showed normal 24-hour urinary free cortisol (62 nanomoles) and serum TSH (1.54 milliUnits per litre). She had hyporeninaemic hypoaldosteronism with a recumbent plasma renin activity 0.3 picomoles per millilitre per hour (normal range 1.1 - 2.7 picomoles per millilitre per hour) and a recumbent plasma aldosterone level less than 55 picomoles per litre (normal range 100 - 450 picomoles per litre). A detailed dietary enquiry revealed that she had been eating excessive numbers of Pontefract Cakes containing liquorice, over the last five years. Since stopping eating liquorice her serum potassium, blood pressure, recumbent plasma renin activity and plasma aldosterone have all normalised.
Liquorice-induced AME is well recognised but only two reports implicate Pontefract Cakes. Liquorice contains glycyrrhizinic acid, a metabolite of which, glycerrhetenic acid, inhibits the enzyme 11-beta hydroxysteroid dehydrogenase type 2. This enzyme is present within the epithelium of the renal distal convoluted tubule and prevents inappropriate activation of renal aldosterone receptors by cortisol through its conversion to cortisone. Liquorice-induced inhibition of the 11-beta hydroxysteroid dehydrogenase type 2 enzyme prevents inactivation of cortisol thereby allowing it to have a mineralocorticoid effect leading to sodium retention, hyporeninaemic hypoaldosteronism, hypertension and hypokalaemia.
This case highlights the importance of a detailed dietary enquiry in any patient presenting with hypertension and hypokalaemia and the potentially lethal but reversible effects of excessive liquorice consumption.