This study is to evaluate the performance characteristics of the seated saline infusion test and the ultra low-dose ACTH stimulation test for the diagnosis of primary aldosteronism.

This is a prospective study (with a target recruitment of 200 participants) designed to evaluate the performance characteristics of the seated saline infusion test and the ultra low-dose ACTH stimulation test for the diagnosis of primary aldosteronism, using disease-specific treatment response as a reference gold standard. Subjects consenting to study participation will undergo a standardized seated saline infusion test, followed by an ultra low-dose ACTH stimulation test. All participants also receive adrenal vein sampling. Individuals who have unilateral disease and desire surgery will receive adrenalectomy (as part of routine care) and the remaining subjects will receive medical treatment with a mineralocorticoid receptor antagonist. Response to targeted treatment will be considered the reference gold standard for the establishing the diagnosis of primary aldosteronism.

Inclusion Criteria:

• Individuals with hypertension
• Individuals with an elevated screening adrenal renin ration (ARR)
• Individuals with high probability features of primary aldosteronism (e.g., resistant hypertension, spontaneous or diuretic-induced hypokalemia, and/or an adrenal nodule) with clinical indications for adrenal vein sampling and surgery (if appropriate).

Exclusion Criteria:

• Individuals with chronic kidney disease (estimated glomerular filtration rate <40 mL/min/1.73m2),
• Individuals with a history of heart failure, chronic edema, uncontrolled severe hypertension (systolic blood pressure >180 and/or diastolic blood pressure >110 mmHg), untreated hypokalemia, cortisol-secreting adrenal adenoma, and/or pheochromocytoma
• Individual who previously received confirmatory testing.

Hypertension individuals suspected of having primary aldosteronism.