Synonyms: Plasma renin
Related tests: ACE, aldosterone
Clinical significance
The proteolytic enzyme renin is produced mainly by the juxtaglomerular cells of the kidney in the form of prorenin and is stored as prorenin or renin granules. Renin is released in response to physiological stimuli such as reduced blood volume, reduced blood pressure and sodium loss. The renin–angiotensin–aldosterone system plays a key role in fluid and salt balance and in regulating blood pressure.
Clinical indications
Renin measurement, together with aldosterone, is useful in the differential diagnosis of primary and secondary hyperaldosteronism.
Sample type
The patient must have a blood sample taken.
Preparation
You must fast for at least 8 hours; a small amount of water is allowed. You must have been standing upright for at least one hour (upright renin) or lying down for at least 2 hours (supine renin).
Notes
Increased renin levels are seen in: secondary aldosteronism, Addison’s disease, low-sodium diet, diuretic use, haemorrhage, chronic kidney failure, salt loss due to gastrointestinal disease, renin-secreting kidney tumours, essential hypertension, hypokalaemia, Bartter syndrome (high renin levels without hypertension) and renal artery stenosis.
Decreased renin levels are seen in: primary aldosteronism, salt retention due to steroid therapy, vasopressin (ADH) therapy, and congenital adrenal hyperplasia with 17-hydroxylase deficiency.