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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Methanol Toxicology

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

A 43-year-old man is brought to the emergency department by his wife. He has headaches, severe abdominal pain with vomiting, and weakness. His vision is also blurry, and he is afraid he is going to lose his vision. His wife is unsure of the duration of his symptoms as she went to bed eight hours ago while he went to work in the garage. When she woke up, she found him lying on the garage floor with an empty bottle of windshield wiper fluid next to him. Which of the following is the most appropriate treatment?

A. Ethanol
B. Penicillamine
C. Deferoxamine
D. NH4Cl
E. Dimercaprol

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Diffusion Capacity for Carbon Monoxide

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

The diffusion capacity of the lung for carbon monoxide (DLCO) is an important test of lung function. I’ve experienced some confusion as I have worked towards understanding this concept, so I wanted to share what I’ve learned.

First, a question:

A 62 year old woman with COPD is evaluated for chronic dyspnea. She has long history of smoking. Respiratory rate is 30; pulse 102; the patient is afebrile. On exam she is cachectic, with distant heart sounds, increased AP diameter of the chest and expiratory wheezing.

What is the most likely finding on pulmonary function test?

  1. Non reversible obstructive pattern with reduced DLCO.
  2. Non reversible obstructive pattern, DLCO within normal.
  3. Reversible obstructive pattern with normal DLCO.
  4. Restrictive pattern.
  5. FEV1/FVC 90% of normal.

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