The four tests for hypertension include aldosterone, cortisol, renin, and adrenocorticotropic hormone. Purpose of the test: It is mainly used to rule out secondary causes of hypertension, such as primary aldosteronism, pheochromocytoma, renal artery stenosis and Cushing’s syndrome. Screening for people: The suitable population is young and middle-aged people with moderate or severe hypertension, as well as patients with refractory hypertension. Aldosterone: It is a steroid hormone, which is part of the renin-angiotensin system. It mainly acts on the kidney to promote the reabsorption of ions and water molecules. Excessive secretion of aldosterone by the adrenal cortex in primary hyperaldosteronism. The main clinical manifestation is hypertension with hypokalemia. Cortisol: It is a type of glucocorticoid. Cortisolism is caused by endocrine disorders resulting in bilateral adrenal cortical hyperplasia or adrenal tumors that secrete excessive cortisol. Increased cortisol can cause an increase in blood pressure. Cushing’s syndrome is a form of cortisolism. Renin: A protein hydrolase that is a component of the renin-angiotensin system. It catalyzes the conversion of angiotensinogen to angiotensin, which raises blood pressure. Adrenocorticotropic hormone: Adrenocorticotropic hormone promotes tissue proliferation in the adrenal cortex as well as the production and secretion of corticosteroids, which promotes elevated blood pressure. Examination Note: The test obtains blood is about 1.8 ml of plasma. The reference values of the four items of hypertension in normal standing are: aldosterone is 40-310pg/mL, cortisol 4.26-24ug/dl, renin 14-38pg/mL, and adrenocorticotropic 7.2-63.4pg/mL.