Licorice Causes High Blood Pressure

This article is part of a series on USMLE Step 1 Study.

I haven’t seen too much about this on USMLE forums, so I thought I would write a quick post on it.

Black licorice contains the active ingredient glycyrrhizin, which is metabolically active.

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Glycyrrhizin INHIBITS the activity of 11-Beta hydroxysteroid dehydrogenase. 11-BHSD, meanwhile, catalyzes the conversion of cortisol to cortisone.

Finally, it’s important to know that cortisone is an inactive metabolite of cortisol. So, the effect of licorice ingestion resembles that which would result simply from having more cortisol on board.

Why does more cortisol cause hypertension? Well, cortisol is active not just at the glucocorticoid receptor, but also at the mineralocorticoid receptor, which is classically reserved for aldosterone. Consequently, 11-BHSD blockade substantially increases mineralocorticoid activity, and thus increases blood pressure. Excess licorice consumption may then be said to cause the syndrome of apparent mineralocorticoid excess, also known as pseudohyperaldosteronism.

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