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Difficulty: HardMedical History Evaluation

A 48-year-old woman is evaluated in the outpatient clinic for persistently elevated blood pressure. She was diagnosed with hypertension six months ago. Her blood pressure today is 168/98 mmHg168/98 \text{ mmHg} despite verified adherence to maximum tolerated doses of amlodipine and valsartan. The patient reports occasional headaches and generalized weakness over the past two months but otherwise feels well. Her past medical history is notable for osteoarthritis and generalized anxiety disorder. Her current medications include amlodipine, valsartan, and acetaminophen as needed. She explicitly denies using nonsteroidal anti-inflammatory drugs. She does not smoke or consume alcohol. BMI is 24 kg/m224 \text{ kg/m}^2. Physical examination reveals a regular heart rate of 78 /min78 \text{ /min} and no abdominal bruits, edema, or focal neurologic deficits.

Laboratory studies show:
Serum sodium: 144 mEq/L144 \text{ mEq/L}
Serum potassium: 2.8 mEq/L2.8 \text{ mEq/L}
Serum chloride: 102 mEq/L102 \text{ mEq/L}
Serum bicarbonate: 30 mEq/L30 \text{ mEq/L}
Serum creatinine: 0.8 mg/dL0.8 \text{ mg/dL}
Plasma renin activity: Undetectable
Plasma aldosterone concentration: <2 ng/dL< 2 \text{ ng/dL}

Which of the following questions is most appropriate to ask next to determine the underlying etiology of this patient's condition?

  1. Do you regularly consume traditional black licorice or herbal supplements for digestion?Answer
  2. B
    Do you often wake up gasping for air or feel excessively sleepy during the day?
  3. C
    Are you taking any herbal supplements containing St. John's wort for your anxiety?
  4. D
    Have you experienced any episodes of palpitations accompanied by a throbbing headache and sweating?
  5. E
    Is there a family history of early-onset kidney disease or renal artery interventions?

Answer

The most appropriate next step is to ask the patient about the consumption of traditional black licorice or herbal supplements containing licorice root.
The correct answer addresses the dietary and supplement history specifically linked to apparent mineralocorticoid excess (AME). This patient presents with resistant hypertension, marked hypokalemia, and metabolic alkalosis. Crucially, her endocrine workup reveals that both plasma renin activity and plasma aldosterone concentration are suppressed. This profile rules out primary hyperaldosteronism (Conn syndrome) and secondary causes of hyperaldosteronism (like renal artery stenosis). Instead, it points to a substance activating the mineralocorticoid receptors independently of aldosterone. Glycyrrhizin, an active compound found in traditional black licorice and various herbal preparations, inhibits the enzyme 11-beta-hydroxysteroid dehydrogenase type 2 (11-beta-HSD2) in the renal collecting duct. This enzyme normally converts active cortisol into inactive cortisone. When it is inhibited, high local levels of cortisol bind to and activate mineralocorticoid receptors. This mimics the action of aldosterone, leading to sodium retention (causing hypertension) and potassium/hydrogen excretion (causing hypokalemia and metabolic alkalosis). The resulting volume expansion suppresses endogenous renin and aldosterone. Therefore, eliciting a history of licorice or specific supplement ingestion is the critical diagnostic step.

Step-by-Step Solution

1
Identify the primary clinical problem from the vignette.
The patient has resistant hypertension complicated by significant hypokalemia and metabolic alkalosis.
Recognizing the triad of hypertension, hypokalemia, and metabolic alkalosis narrows the differential diagnosis to mineralocorticoid excess states.
2
Interpret the specific endocrine laboratory data.
Both plasma renin activity and plasma aldosterone concentration are profoundly suppressed.
This specific profile rules out primary hyperaldosteronism (where aldosterone would be high and renin low) and secondary hyperaldosteronism (where both would be high).
3
Formulate a differential diagnosis for hypertension with hypokalemia and low renin/low aldosterone.
The findings indicate a state of Apparent Mineralocorticoid Excess (AME). In an adult without a lifelong history of hypertension, this is almost exclusively an acquired condition.
Acquired AME is caused by an exogenous substance that acts on the mineralocorticoid receptor or prevents cortisol degradation.
4
Connect the pathophysiology to the medical history evaluation.
Glycyrrhizin, found in traditional black licorice and some herbal supplements (often used for dyspepsia), inhibits the enzyme responsible for cortisol degradation in the kidneys.
Asking about licorice or specific herbal supplement ingestion directly targets the underlying etiology of her acquired AME.

Key Concept

Evaluating the history for exogenous causes of apparent mineralocorticoid excess (e.g., licorice ingestion) when labs show hypertension, hypokalemia, low renin, and low aldosterone.
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Topics

Medical History Evaluation

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