In a 25-year-old man with resistant hypertension, hypokalemia, metabolic alkalosis, and a family history of stroke, which investigation is appropriate to evaluate the cause of his uncontrolled blood pressure?

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Last updated: September 30, 2026 • View editorial policy

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Renin-Aldosterone Ratio (Answer A)

In this 25-year-old man with resistant hypertension, hypokalemia, and metabolic alkalosis, you should order a renin-angiotensin ratio (plasma aldosterone-renin ratio, ARR) to screen for primary aldosteronism, which is the most likely diagnosis and the most common cause of secondary hypertension in this clinical scenario 1, 2.

Clinical Reasoning

This patient presents with the classic triad of primary aldosteronism:

  • Resistant hypertension (uncontrolled on two medications at age 25)
  • Hypokalemia (low potassium)
  • Metabolic alkalosis (low bicarbonate/low pH suggests this, though typically pH would be elevated in alkalosis)

The combination of young age, resistant hypertension, and spontaneous hypokalemia makes primary aldosteronism highly likely, with prevalence reaching 17.8% in young-onset hypertension and 20-30% in resistant hypertension 2.

Why Renin-Aldosterone Ratio First

The 2025 Endocrine Society guidelines explicitly recommend ARR as the primary screening tool for primary aldosteronism in patients with resistant hypertension and/or hypokalemia 1. The ARR will show:

  • Elevated aldosterone (typically >15 ng/dL by LC-MS/MS or >20 ng/dL by immunoassay)
  • Suppressed renin (PRA <0.2 ng/mL/h or DRC <2 mU/L)

This pattern confirms autonomous aldosterone production independent of the renin-angiotensin system 3, 4.

Why Not the Other Options

Options B, C, and D (metanephrines and catecholamines) are used to screen for pheochromocytoma, which typically presents with:

  • Episodic hypertension (not sustained resistant hypertension)
  • Paroxysmal symptoms (headaches, palpitations, sweating)
  • Hypokalemia is NOT a feature of pheochromocytoma

The presence of hypokalemia with metabolic alkalosis essentially rules out pheochromocytoma as the primary diagnosis and points directly toward mineralocorticoid excess (primary aldosteronism) 5.

Important Caveats

  • Medication interference: Beta-blockers and centrally acting alpha-2 agonists can suppress renin and cause false-positive ARR results. If the patient is on these medications, consider repeating the test after 2-week withdrawal if safe 1.
  • Potassium correction: Ideally, correct hypokalemia before testing, as low potassium can suppress aldosterone secretion and cause false-negative results 6.
  • Confirmatory testing: If ARR is positive but aldosterone levels are intermediate (5-15 ng/dL), confirmatory testing with saline infusion test or other suppression tests may be needed 1.

Next Steps After Positive ARR

Once primary aldosteronism is confirmed:

  1. Adrenal CT imaging to identify unilateral adenoma vs bilateral hyperplasia
  2. Adrenal venous sampling if surgical candidate to lateralize aldosterone production
  3. Treatment: Unilateral adenoma → surgical adrenalectomy; bilateral disease → mineralocorticoid receptor antagonists (spironolactone/eplerenone) 1, 3

The family history of stroke is particularly concerning, as untreated primary aldosteronism carries significantly increased cardiovascular risk, including stroke, with MACE rates of 13.6% at 5.8 years 2.

References

1
Guideline

primary aldosteronism: an endocrine society clinical practice guideline.

The Journal of clinical endocrinology and metabolism, 2025

4
Research

Resistant hypertension and aldosteronism.

Current hypertension reports, 2007

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