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Difficulty: MediumEndocrinology and Metabolism

Match each clinical vignette describing a patient with an endocrine or renal-related blood pressure/electrolyte abnormality to their expected pathophysiologic laboratory profile.

  • A 45-year-old man with treatment-resistant hypertension, muscle cramps, and spontaneous hypokalemia.Low plasma renin activity, High serum aldosterone
  • A 26-year-old woman with severe hypertension, hypokalemia, and a right-sided abdominal systolic-diastolic bruit.High plasma renin activity, High serum aldosterone
  • A 50-year-old man with hypertension, hypokalemia, and a history of consuming large amounts of natural black licorice extract daily.Low plasma renin activity, Low serum aldosterone
  • A 32-year-old woman with chronic fatigue, weight loss, salt craving, hyperpigmentation, and hyperkalemia.High plasma renin activity, Low serum aldosterone

Answer

The correct matches depend on analyzing the renin-angiotensin-aldosterone axis feedback loop: autonomous adrenal aldosterone suppresses renin; renal ischemia stimulates renin which raises aldosterone; mineralocorticoid-receptor activation by exogenous substances suppresses both; and adrenal destruction eliminates aldosterone, causing a massive compensatory rise in renin.
Each clinical presentation uniquely disrupts the RAAS axis. By establishing the primary site of disease (adrenal vs. renal vs. exogenous) and following the feedback loops (volume status affecting renin), the corresponding lab profiles can be accurately mapped.

Step-by-Step Solution

1
Analyze each patient vignette to determine the primary source of the pathology.
Identify if the problem is in the adrenal gland (Conn syndrome, Addison disease), the renal artery (fibromuscular dysplasia), or exogenous/mimicker (licorice ingestion).
Knowing the etiology allows you to predict where the hormonal axis is initially disrupted.
2
Determine the impact of the primary pathology on circulating volume and blood pressure.
Conn syndrome, fibromuscular dysplasia, and licorice ingestion cause volume expansion (hypertension). Addison disease causes volume depletion (hypotension).
Plasma renin activity is tightly controlled by renal perfusion and circulating volume.
3
Apply negative and positive feedback principles to the Renin-Angiotensin-Aldosterone System (RAAS).
Volume expansion suppresses renin (except in fibromuscular dysplasia, where ischemia artificially acts as the primary driver of renin). Aldosterone is high if it is the primary tumor product or stimulated by renin, but low if destroyed (Addison's) or suppressed by a mimicker (licorice).
This logical sequence perfectly predicts the hormonal laboratory profile for each diagnosis.

Key Concept

Pathophysiologic regulation and feedback of the Renin-Angiotensin-Aldosterone System in Endocrine Hypertension and Adrenal Insufficiency
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Topics

Endocrinology and Metabolism

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