Primary aldosteronism (PA) is the most common cause of secondary hypertension. Liquid chromatography - tandem mass spectrometry (LC-MS/MS) is more accurate than the traditional radioimmunoassay in measuring aldosterone. This study aims to establish a more precise diagnostic threshold for the oral sodium loading test (OSLT) by using LC-MS/MS to measure urinary aldosterone levels. We will combine the biochemical results of OSLT and other data from healthy volunteers and suspected PA patients to determine a new 24-hour urinary aldosterone threshold. We expect to improve the diagnostic accuracy of PA, helping clinicians identify this curable cause of hypertension earlier and more accurately, and achieving precise treatment.

Inclusion criteria for the normal control group: Age 18-70 years old, BMI: 18.5-23.9kg/m ²，gender not restricted. blood pressure: 100-120/60-80mmHg. no history of hypertension. No abnormal nodules found in adrenal CT. Previous blood potassium and electrocardiogram were all within normal ranges., No history of liver or kidney dysfunction, malignant tumors, metabolic diseases or cardiovascular diseases, and no medication used.

Exclusion criteria: Those with a family history of hypertension or with clinical manifestations of secondary hypertension. Those who have been taking drugs that may affect the RAAS system for a long time (such as contraceptives, steroids, etc.). Those with cardiac dysfunction or severe arrhythmia and unable to tolerate the test.

Patients with suspected primary aldosteronism in the outpatient setting. Inclusion criteria: Patients with suspected primary aldosteronism in the outpatient setting. Willing to undergo 4-week spironolactone treatment and cooperate with follow-up.

Exclusion criteria: Patients who did not complete the oral sodium loading test. Patients with Cushing's syndrome or other endocrine tumors. Patients allergic to spironolactone or with contraindications for its use (such as severe hyperkalemia, eGFR < 30).History of liver or kidney dysfunction, coexisting severe cardiovascular or cerebrovascular diseases, history of malignant tumors, other types of endocrine hypertension (hyperthyroidism, pheochromocytoma, Cushing's syndrome, etc.), renal artery stenosis, hypokalemia caused by other factors (renal tubular acidosis, Bartter syndrome, Gitelman syndrome, etc.), diabetes with HbA1c > 7.0% or currently using or having used insulin or SGLT2 inhibitor drugs, taking special medications such as glucocorticoids, immunosuppressants, oral contraceptives, etc.

1）Healthy Controls to establish physiological suppression limits.2) Patients with suspected PA undergo oral sodium loading test to determine the cut-off point.