Renin is also called angiotensinogenase; it’s an enzyme produced by the kidneys to control aldosterone production. It’s also essential in the renin–angiotensin aldosterone system (RAAS) which maintains your body’s fluid balance and blood pressure. This system regulates blood plasma volume, lymph and interstitial fluid (the fluid which surrounds the cells in the body) and controls constriction of the arteries and blood vessels.
Three factors stimulate the secretion of renin:
- When a drop in arterial blood pressure is detected by pressure-sensitive receptors in the arteries
- When a drop in salt level is detected in the kidneys
- When activity is detected in the sympathetic nervous system activity
Renin’s primary function is to increase blood pressure to maintain healthy blood flow to the kidneys. It’s secreted by specialized kidney cells that can detect changes in blood pressure through stretch receptors in the vascular walls. Renin starts a chain reaction that makes the hormone called angiotensin, which makes small blood vessels narrower and stimulates the adrenal glands to secrete aldosterone. Aldosterone signals the kidneys to hold on to fluid and salt. Both can increase blood pressure. When this process is out of balance, blood pressure can rise to dangerous levels.
Hypertension and the renin test
If you experience high blood pressure (hypertension), your doctor needs to find out the reason why to prescribe the correct treatment. A renin test is used to discover what’s happening in the body that may be causing it. The doctor might order this kind of test if high blood pressure starts when you’re young or medication hasn’t kept it under control. Because renin is involved in aldosterone metabolism, an aldosterone test may be conducted at the same time.
Your test results will tell the doctor if your renin levels are high, low, or healthy. Either high or low levels could help explain why your blood pressure is too high.
More on this test and how it affects blood pressure and water retention here
What the renin and ALD test results may mean:
- Excess renin with normal aldosterone levels could mean that you’re salt-sensitive
- Low renin and excess aldosterone may indicate that your adrenal glands aren’t functioning properly
- If both renin and ALD are high, it may be a sign of kidney trouble
Whatever the results are, they will help the doctor decide which drugs or treatments are best to get your blood pressure under control.