According to 2010 Chinese guidelines for the management of essential hypertension (EH), EH was defined as systolic BP (SBP) ≥140 mm Hg, diastolic BP (DBP) ≥90 mm Hg, and use of antihypertensive medicine within 2 weeks and excluded from PA through ARR or diagnostic testing.

Patients were confirmed to be diagnosed with primary aldosteronism (PA) in accordance with the Endocrine Society Clinical Practice Guideline criteria. Antihypertensive drugs that may affect the renin-angiotensin-aldosterone system (RAAS) were discontinued for at least 2-4 weeks. Patients with an aldosterone-to-renin ratio (ARR) > 3.7 (ng/dL) further underwent one of the following confirmatory tests: saline infusion test (infusion of 2 L isotonic saline within 4 h) or captopril-inhibition test (oral administration of 50 mg captopril). Adrenal CT scan and adrenal vein sampling (AVS) were performed for PA subtype classification. Patients with IHA were determined based on the absence of obvious adenoma on adrenal CT and bilateral aldosterone overproduction.

Patients were confirmed to be diagnosed with primary aldosteronism (PA) in accordance with the Endocrine Society Clinical Practice Guideline criteria. Antihypertensive drugs that may affect the renin-angiotensin-aldosterone system (RAAS) were discontinued for at least 2-4 weeks. Patients with an aldosterone-to-renin ratio (ARR) > 3.7 (ng/dL) further underwent one of the following confirmatory tests: saline infusion test (infusion of 2 L isotonic saline within 4 h) or captopril-inhibition test (oral administration of 50 mg captopril). Adrenal CT scan and adrenal vein sampling (AVS) were performed for PA subtype classification. Patients with APA were identified based on macroadenoma >1 cm on adrenal CT, unilateral hypersecretion of aldosterone, and pathological confirmation.

Metabolomics is a rapidly evolving high-throughput technology that allows the measurement of the entire complement of metabolites generated by biochemical reactions under certain conditions in biological fluids or tissues. This technology has been used extensively to identify biomarkers in various cancers, nervous system diseases, cardiovascular diseases, pituitary diseases, and other diseases. The identification of biomarkers can be clinically useful for a more accurate diagnosis, prognosis, and treatment choice as well as disease monitoring. Among mass spectrometry (MS) methods, liquid chromatography- mass spectrometry (LC-MS) has been recognized as a robust metabolomics tool and has been widely applied in metabolite identification and quantification due to its high sensitivity, peak resolution, and reproducibility.

The differentially expressed metabolites between primary aldosteronism (PA) and essential hypertension (EH) will be identified by untargeted metabolomics. The differentially expressed metabolites with good discriminative capability for determination of PA from EH can serve as biomarkers for PA diagnosis.

The differentially expressed metabolites between idiopathic aldosteronism (IHA) and aldosterone-producing adenoma (APA) will be identified by untargeted metabolomics. The differentially expressed metabolites with good discriminative capability for determination of APA from IHA can serve as biomarkers for PA subtype classification.

The predictive models will be constructed through the application of machine learning, integrating clinical data with differentially expressed metabolites for the diagnosis and subtype classification of PA