Plasma renin activity measurement is used to investigate primary and secondary hyperaldosteronism.
Renin is a proteolytic enzyme that is synthesized, stored and secreted by parasympathetic kidney cells and plays an important role in regulating blood pressure, potassium levels and fluid volume balance. The activity of the renin-angiotensin-aldosterone systems results in the production of angiotensin II, a potent vasoconstrictor, that stimulates aldosterone production in the adrenal cortex. Reduced renal blood flow stimulates renin secretion and increases aldosterone secretion. Blood loss and sodium depletion also stimulate the release of renin. Changing the body's position from supine to upright has been found to increase the level of renin. Sodium intake also affects renin levels: high sodium intake lowers renin levels, while reduced sodium triggers release of elevated renin levels.
Plasma renin activity (PRA) measurement is used in the differential diagnosis of hypertension. Hypertensive patients with low renin activity are likely to have a fluid volume imbalance while people with high renin activity are probably hypertensive due to the vasoconstrictive action of angiotensin, a condition known as renal hypertension. Patients with essential hypertension may check their renin and aldosterone levels to assess whether they are salt sensitive, which causes low renin levels with normal aldosterone levels. This helps in choosing the right medication.
Possible Interpretations of Pathological Values
- Increase: Addison's disease, aldosteronism (secondary), Bartter's syndrome, chronic kidney failure, cirrhosis, Conn syndrome, upright posture for 4 hours (doubling), idiopathic hypertension (rare), hypokalaemia, second half of menstrual cycle, low sodium diet, nephropathy (with sodium loss), normal pregnancy, pheochromocytoma, renal hypertension, renin-producing renal tumors, graft rejection. Medications: Diazoxide, estrogen, furosemide, guanethidine sulfate, hydralazine hydrochloride, minoxidil, sodium nitroprussate, saralazine, spironolactone, thiazides
- Decrease: Congenital adrenal hyperplasia, Cushing's syndrome, elderly, idiopathic hypertension, fasting, high sodium diet, primary hyperaldosteronism, fluid overload, weight loss, sodium-retaining steroids, salicylates
Laboratory test results are the most important parameter for the diagnosis and monitoring of all pathological conditions. 70%-80% of diagnostic decisions are based on laboratory tests. Correct interpretation of laboratory results allows a doctor to distinguish "healthy" from "diseased".
Laboratory test results should not be interpreted from the numerical result of a single analysis. Test results should be interpreted in relation to each individual case and family history, clinical findings and the results of other laboratory tests and information. Your personal physician should explain the importance of your test results.
At Diagnostiki Athinon we answer any questions you may have about the test you perform in our laboratory and we contact your doctor to get the best possible medical care.