Hypertension with low potassium in a 38-year-old woman — case discussion

Presentation

Practice case (not a real patient). A 38-year-old woman in Australia has hypertension confirmed by home BP monitoring (average 152/96 mmHg). She is not obese and reports no snoring, daytime sleepiness, palpitations or sweating.^[1] She takes a long-acting dihydropyridine calcium channel blocker (CCB) and hydrochlorothiazide. Her serum potassium is 3.1 mmol/L, and her creatinine, eGFR, urinalysis, TSH and calcium are normal.^[2][1]

Step 1 — Should she be screened, and for what?

Discussion:

• Yes. ESC 2024 recommends comprehensive screening for the main causes of secondary hypertension in adults diagnosed with hypertension before the age of 40 years (Class I, Level B); the OSA-first exception applies only to obese young adults.^[1]
• AHA/ACC 2025 recommends primary aldosteronism screening in adults with hypertension and any of a list of conditions that includes hypokalaemia, spontaneous or diuretic induced (COR 1, LOE C-EO), and ESC 2024 says screening by renin and aldosterone should be considered in all adults with confirmed hypertension (Class IIa, Level B).^[2][1]
• Her normal TSH and calcium cover the hyperthyroidism and hyperparathyroidism screening listed in ESC 2024 Table 8.^[1]
• ESC 2024 says fibromuscular dysplasia should be considered as a cause of secondary hypertension in young women, and its Table 13 screens for renovascular hypertension with renal Doppler ultrasound and abdominal CT angiogram or MRI; her renal Doppler ultrasound is normal.^[1]

Step 2 — Preparing and reading the aldosterone-to-renin ratio

• AHA/ACC 2025 recommends continuing most antihypertensive medications other than MRAs before initial screening (COR 1, LOE C-EO), and asks for serum potassium in the normal range to avoid false-negative testing.^[2]
• Her potassium is corrected into the normal range (4.0 mmol/L), and she continues both drugs.^[2]
• ESC 2024 says long-acting CCBs do not interfere with the ratio; AHA/ACC 2025 says thiazide-type diuretics, its term for hydrochlorothiazide, chlorthalidone and indapamide, can stimulate both renin and aldosterone.^[1][2]
• Her plasma aldosterone is 24 ng/dL and renin activity 0.3 ng/mL/h, a ratio of 80.^[2]
• AHA/ACC 2025: renin activity is typically suppressed (<1 ng/mL/h) in primary aldosteronism, most data support a plasma aldosterone of at least 10 ng/dL to call the test positive (with additional evaluation possibly indicated if renin activity is suppressed), and the most commonly used ratio cut-off is 30, so this screen is positive while she takes a thiazide-type diuretic, which AHA/ACC 2025 says can stimulate both renin and aldosterone.^[2]

Step 3 — Referral, confirmation and lateralisation

• AHA/ACC 2025 recommends referral to a hypertension specialist or endocrinologist after a positive screen (COR 1, LOE C-EO).^[2]
• The diagnosis may require an aldosterone suppression test such as an IV saline suppression test or oral salt-loading test (AHA/ACC 2025); her IV saline suppression test confirms primary aldosteronism.^[2]
• Adrenal CT shows a 1.8 cm right adrenal nodule; AHA/ACC 2025 says adrenal imaging should be considered once primary aldosteronism is confirmed, to exclude a large mass with features suggestive of malignancy (size >4 cm, imaging characteristics).^[2]
• She would like surgery if it is an option, so she is referred for adrenal venous sampling (AHA/ACC 2025), which the Australian and New Zealand working group calls the current recommended procedure for identifying unilateral subtypes.^[2][6]
• The 2025 Endocrine Society guideline suggests a 1-mg overnight dexamethasone suppression test in everyone with primary aldosteronism and an adrenal adenoma.^[4]
• Sampling shows unilateral right-sided aldosterone excess.^[2]

Step 4 — Treatment

• AHA/ACC 2025: unilateral excess on adrenal venous sampling leads to referral for unilateral laparoscopic adrenalectomy; ESC 2024 says surgical removal of the affected gland is typically considered for unilateral disease unless the patient is older or has comorbidities of concern.^[2][1]
• She has a right laparoscopic adrenalectomy.^[2]
• AHA/ACC 2025 says treating primary aldosteronism, with an MRA or unilateral adrenalectomy if indicated, is associated with resolution of hypokalaemia, lower BP, fewer antihypertensive drugs required and improved parameters of impaired cardiac and kidney function.^[2]

Step 5 — What if sampling had shown bilateral disease?

• AHA/ACC 2025: bilateral excess, unsuitability for surgery or no interest in surgery leads to an MRA (for example spironolactone or eplerenone).^[2]
• ESC 2024: spironolactone usually 50–100 mg once daily, titrated up to 300–400 mg once daily if necessary; eplerenone is less potent and needs twice-daily dosing but causes less gynaecomastia and erectile dysfunction in men.^[1]
• Endocrine Society 2025: suggests spironolactone over other MRAs given its lower cost and greater availability; all MRAs titrated to equivalent potencies are anticipated to have similar efficacy, so MRAs with greater mineralocorticoid receptor specificity and fewer androgen- and progesterone-receptor side effects may be preferred in some situations. It also suggests monitoring renin on treatment and titrating the MRA to increase renin if hypertension remains uncontrolled with suppressed renin.^[4]

Take-home points

• Hypertension diagnosed before 40 earns comprehensive screening for the main causes, starting with a sleep apnoea evaluation if the patient is obese (ESC 2024, Class I, Level B).^[1]
• Bring potassium into the normal range before the ratio and read the result against the drug list (AHA/ACC 2025; ESC 2024 Table 12).^[2][1]
• Confirm, then lateralise by adrenal venous sampling before adrenalectomy (AHA/ACC 2025).^[2]