The Most Common Curable Cause of High Blood Pressure That Rarely Gets Tested

Primary aldosteronism is the most common curable hormonal cause of high blood pressure, and a simple blood test, the aldosterone-to-renin ratio, can flag it. Yet fewer than one in fifty people with resistant hypertension ever get that test. In 2025 the Endocrine Society moved toward screening everyone with high blood pressure, because the condition is far more common than the old picture assumed. That gap between how treatable this is and how seldom it is looked for is the whole story of this article.

The practical stakes are high. When aldosterone runs high independently of the body's normal controls, it raises blood pressure and quietly damages the heart, kidneys, and blood vessels beyond what the blood pressure number alone would predict, and much of that risk can be reversed once the cause is named.

What aldosterone is supposed to do

Aldosterone is a hormone made by the adrenal glands, two small caps of tissue that sit above the kidneys. Its normal job is to manage salt and water. When the body senses low blood volume or low sodium, it releases an enzyme called renin, renin sets off a cascade, and aldosterone rises to tell the kidneys to hold onto salt and water. Blood pressure comes back up. When volume is adequate, renin falls, aldosterone falls, and the system rests.

That feedback loop is the key to the whole condition. Renin is meant to be the accelerator and aldosterone the response. In primary aldosteronism the adrenal glands produce aldosterone on their own, without waiting for renin's signal. The result is a hormone stuck in the on position while the accelerator it should answer to has been released.

Why it is more common than the textbooks said

For decades primary aldosteronism was taught as a rare cause of hypertension, something to consider only in a patient with high blood pressure and low potassium. That framing turned out to be far too narrow. A landmark cross-sectional study by Brown and colleagues, published in Annals of Internal Medicine in 2020, measured renin-independent aldosterone production across the full range of blood pressure. Biochemically overt primary aldosteronism was present in roughly 16 percent of people with stage 1 hypertension and about 22 percent of those with resistant hypertension, and even a meaningful fraction of people with normal blood pressure showed some degree of renin-independent aldosterone production.

The important reframing from that work is that primary aldosteronism behaves less like a rare on-or-off disease and more like a spectrum. There is a continuum of aldosterone production that runs partly free of renin control, and it tends to track with the severity of hypertension. Low potassium, the classic clue, shows up in only a minority of cases, which is exactly why a rule that waited for low potassium missed most people who had the condition.

The aldosterone-to-renin ratio, in plain terms

The screening test is a pair of blood measurements: aldosterone and renin, read together as a ratio. The logic follows directly from the biology. If aldosterone is high while renin is suppressed, that combination points to aldosterone being produced independently rather than in response to a normal signal. A high ratio, driven by suppressed renin, is the fingerprint the test is designed to catch.

A positive screen is not a diagnosis. It is a flag that says the pathway deserves a closer look, sometimes with a confirmatory step and, in selected cases, imaging or specialized adrenal vein sampling to determine whether one gland or both are responsible. What matters for the general reader is that the entry point is a standard blood draw, not an exotic procedure, and it can be done in ordinary practice.

One practical barrier deserves mention. Several blood pressure medicines nudge aldosterone and renin levels, which long made clinicians hesitant to test without an elaborate medication washout. A 2026 review in Hypertension by Owei, Wachtel, and Cohen, aligning the recent guidelines, notes that the ratio keeps high sensitivity and a high negative predictive value even without stopping most medications. In plain terms, a negative result is trustworthy enough that the fear of imperfect conditions is a weak reason not to test at all.

Why it so rarely gets tested

Here is the uncomfortable part. Despite guidelines that have recommended screening in resistant hypertension for years, the testing almost never happens. Multiple health-system studies find that screening rates among people with resistant hypertension sit at roughly 2 percent or lower, and even among patients with the textbook combination of hypertension plus low potassium, only a small single-digit percentage are ever screened.

The reasons are ordinary rather than sinister. A busy visit has a short list of priorities, blood pressure often gets treated by the numbers with another pill added, and the ratio test carries a reputation for being finicky. The consequence is that a treatable cause hides in plain sight while treatment aims at the symptom.

What changed in 2025

The Endocrine Society published an updated clinical practice guideline in The Journal of Clinical Endocrinology and Metabolism in 2025 that widened the door considerably. Rather than reserving screening for resistant cases or those with low potassium, it moved toward screening all individuals with hypertension, regardless of severity or potassium level, using aldosterone and renin measurements. The 2026 Hypertension review places this alongside other recent guidelines that are converging on broader testing, with major cardiology guidance now endorsing screening at least in more severe hypertension.

The reasoning is a direct consequence of the prevalence data. If the condition is common across the whole range of hypertension and the entry test is a blood draw, then narrowing screening to a small subgroup guarantees that most cases stay hidden. The guideline also leans toward more pragmatic pathways, so that a positive screen can lead to targeted treatment without every patient being routed through the longest possible workup.

This is educational information, not medical advice, and decisions about testing and treatment belong with a person and their own clinician. The single message worth carrying out of it is a question worth asking: if your blood pressure is high, and especially if it is hard to control, has anyone measured your aldosterone and renin?