An important enzyme produced by the kidneys is renin. This enzyme is part of the renin-angiotensin-aldosterone system, and it plays an important role in the regulation of blood pressure in the body, as noted by Inner Body. The kidneys also produce calcitriol and erythropoietin.
The kidneys, which are bean-shaped organs, have many different functions in the body, including the removal of waste products, regulation of sodium and potassium, production of hormones that regulate calcium metabolism and balancing its fluid content. Other functions of the kidneys are the regulation of blood pressure and secretion of renin, as stated by Inner Body.
The kidneys regulate blood pressure by controlling the amounts of sodium ions or fluid excreted from the body. When there is a decrease in blood pressure, the kidneys secrete renin, which in turn leads to the formation of angiotensin and the adrenal glands releasing the hormone aldosterone. This hormone then causes the kidneys to increase the body's blood pressure by reabsorbing sodium ions and water.
A renin blood test can be useful when patients have hypertension. A low renin test result can be an indication of a salt-sensitive patient with hypertension, notes the National institutes of Health's MedlinePlus. However, a low renin test result can also occur if there is an overproduction of aldosterone by the adrenal glands. High renin test results can be caused by a kidney tumor, dehydration, or adrenal gland insufficiency.