'Game Changer': Aldosterone-Driven Hypertension More Common Than Thought

Mitchel L. Zoler

May 28, 2020

Roughly 16%-22% of patients with hypertension appeared to have primary aldosteronism as the likely major cause of their elevated blood pressure, in an analysis of about 1,000 Americans, which is a much higher prevalence than previously appreciated and a finding that could potentially reorient both screening for aldosteronism and management for this subset of patients.

"Our findings show a high prevalence of unrecognized yet biochemically overt primary aldosteronism [PA] using current confirmatory diagnostic thresholds. They highlight the inadequacy of the current diagnostic approach that heavily relies on the ARR [aldosterone renin ratio] and, most important, show the existence of a pathologic continuum of nonsuppressible renin-independent aldosterone production that parallels the severity of hypertension," wrote Jennifer M. Brown, MD, and coinvestigators in a report published in Annals of Internal Medicine on May 25. "These findings support the need to redefine primary aldosteronism from a rare and categorical disease to, instead, a common syndrome that manifests across a broad severity spectrum and may be a primary contributor to hypertension pathogenesis," they wrote in the report.

The results, showing an underappreciated prevalence of both overt and subtler forms of aldosteronism that link with hypertension, won praise from several experts for the potential of these findings to boost the profile of excess aldosterone as a common and treatable cause of high blood pressure, but opinions on the role for the ARR as a screen to identify affected patients were more mixed.

"ARR is still the best screening approach we have" for identifying people who likely have PA, especially when the ratio threshold for finding patients who need further investigation is reduced from the traditional level of 30 ng/dL to 20 ng/dL, commented Michael Stowasser, MBBS, professor of medicine at the University of Queensland in Brisbane, Australia, and director of the Endocrine Hypertension Research Centre at Greenslopes and Princess Alexandra Hospitals in Brisbane. "I strongly recommend ARR testing in all newly diagnosed hypertensives."

The study results "showed that PA is much more common than previously perceived, and suggest that perhaps PA in milder forms than we typically recognize contributes more to 'essential' hypertension than we previously thought," said Anand Vaidya, MD, senior author of the report and director of the Center for Adrenal Disorders at Brigham and Women's Hospital in Boston. The researchers found adjusted PA prevalence rates of 16% among 115 untreated patients with stage 1 hypertension (130-139/80-89 mm Hg), 22% among 203 patients with untreated stage 2 hypertension (at least 140/90 mm Hg), and 22% among 408 patients with treatment-resistant hypertension. All three prevalence rates were based on relatively conservative criteria that included all 726 patients with hypertension in the analysis (which also included 289 normotensive subjects) regardless of whether or not they also had low levels of serum renin. These PA prevalence rates were also based on a "conservative" definition of PA, a level of at least 12 mcg excreted in a 24-hour urine specimen.

When the researchers applied less stringent diagnostic criteria for PA or focused on the types of patients usually at highest risk for PA because of a suppressed renin level, the prevalence rates rose substantially and, in some subgroups, more than doubled. Of the 726 people with hypertension included in the analysis, 452 (62%) had suppressed renin (seated plasma renin activity < 1.0 mcg/L per hour or supine plasma renin activity < 0.6 mcg/L per hour). Within this subgroup of patients with suppressed renin, the adjusted prevalence of PA by the threshold of 24-hour urine aldosterone secretion of at least 12 mcg was 52% in those with treatment-resistant hypertension; among patients with stage 1 or 2 hypertension the adjusted prevalence rates were just slightly above the rates in the entire study group. But among patients with suppressed renin who were judged to have PA by a more liberal definition of at least 10 mcg in a 24-hour urine sample, the adjusted prevalence rates were 27% among untreated stage 1 hypertensives, 40% among untreated stage 2 patients, and 58% among treatment-resistant patients, the report showed.

A Role for Subtler Forms of Aldosteronism

Defining PA as at least 12 mcg secreted in a 24-hour urine collection "is relatively arbitrary, and our findings show that it bisects a continuous distribution. How we should redefine PA is also arbitrary, but step one is to recognize that many people have milder forms of PA" that could have an important effect on blood pressure, Dr. Vaidya said in an interview.

"This is the very first study to show that aldosterone may be contributing to the hypertensive process even though it is not severe enough to be diagnosed as PA according to current criteria," said Robert M. Carey, MD, a cardiovascular endocrinologist and professor of medicine at the University of Virginia in Charlottesville and a coauthor on the new report. "More patients than we have ever known have an aldosterone component to their hypertension," Dr. Carey said in an interview.

The new report on the prevalence of unrecognized PA in hypertensive patients "is a game changer," wrote John W. Funder, MD, professor of medicine at Monash University in Clayton, Australia, in an editorial published along with the new report. In the editorial, he synthesized the new findings with results from prior reports to estimate that excess aldosteronism could play a clinically meaningful role in close to half of patients with hypertension, although Dr. Stowasser called this an "overestimate." The new results also showed that "the single spot measurement of plasma aldosterone concentration, which clinicians have used for decades to screen for primary aldosteronism, is not merely useless but actually misleading. The authors cautioned readers about the uncertain representativeness of the study population to the U.S. population, but I believe that the findings are generalizable to the United States and elsewhere," Dr. Funder wrote. "The central problem is that plasma aldosterone concentration is a very poor index of total daily aldosterone secretion. A single morning spot measurement of plasma aldosterone cannot take into account ultradian variation in aldosterone secretion."

The Importance of Finding Excess Aldosterone

Identifying patients with hypertension and PA, as well as hypertensives with excess aldosterone production that may not meet the traditional definition of PA, is especially important because they are excellent candidates for two forms of targeted and very effective treatments that have a reliable and substantial impact on lowering blood pressure in these patients. One treatment is unilateral adrenal gland removal in patients who produce excess aldosterone because of benign adenomas in one adrenal gland, which accounts for "approximately 30%" of patients with PA. "Patients with suspected PA should have an opportunity to find out whether they have a unilateral variety and chance for surgical cure," said Dr. Stowasser in an interview. "Patients with PA do far better in terms of blood pressure control, prevention of cardiovascular complications, and quality of life if they are treated specifically, either medically or particularly by surgery."

The specific medical treatment he cited refers to one of the mineralocorticoid receptor antagonist (MRA) drugs, spironolactone and eplerenone (Inspra), because mineralocorticoid receptor blockade directly short-circuits the path by which aldosterone increases blood pressure. "We're advocating earlier use of MRAs" for hypertensive patients identified with excess aldosterone production, said Dr. Carey. He noted that alternative, nonsteroidal MRAs, such as finerenone, have shown promise for efficacy levels similar to what spironolactone provides but without as many adverse effects because of greater receptor specificity. Finerenone and other nonsteroidal MRAs are all currently investigational. Spironolactone and eplerenone both cause hyperkalemia, although treatment with potassium binding agents can blunt the risk this poses. Spironolactone also causes bothersome adverse effects in men, including impotence and gynecomastia because of its action on androgen receptors, effects that diminished with eplerenone, but eplerenone is not as effective as spironolactone, Dr. Carey said.

Study Details

The new study ran a post hoc analysis on data collected in five independent studies run at centers in four U.S. locations: Birmingham, Ala.; Boston; Charlottesville, Va.; and Salt Lake City. The studies included a total of 1,846 adults, mostly patients with hypertension of varying severity but also several hundred normotensive people. Data on 24-hour sodium excretion during an oral sodium suppression test were available for all participants, and the researchers excluded 831 people with an "inadequate" sodium balance of less than 190 mmol based on this metric, leaving a study population of 1,015. The researchers acknowledged the limitation that the study participants were not representative of the U.S. population.

The analysis included 289 normotensive people not on any blood pressure–lowering medications, and 239 fit the definition of having suppressed renin. The adjusted prevalence of aldosteronism at the level of at least 12 mcg excreted in a 24-hour urine specimen was 11% among all 289 normotensive subjects and 12% among the 239 with suppressed renin. When the definition of aldosteronism loosened to at least 10 mcg excreted during 24 hours the adjusted prevalence of excess aldosterone among normotensives increased to 19% among the entire group and 20% among those with suppressed renin. This finding may have identified a primordial phase of nascent hypertension that needs further study but may eventually provide a new scenario for intervention. "If a normotensive person has compliant arteries and healthy kidneys they can handle the excess salt and volume load of PA," but when compensatory mechanisms start falling short through aging or other deteriorations, then blood pressure starts to rise, suggested Dr. Vaidya.

Whom to Screen for Aldosteronism and How

While several experts agreed these findings added to an existing and growing literature showing that PA is common and needs greater diagnostic attention, they differed on what this may mean for the specifics of screening and diagnosis, especially at the primary care level.

"Our results showed more explicitly that excess aldosterone exists on a broad severity spectrum and can't be regarded as a categorical diagnosis that a patient either has or does not have. The hard part is figuring out where we should begin interventions," said Dr. Vaidya.

"This publication will hopefully increase clinician awareness of this common and treatable form of hypertension. All people with high blood pressure should be tested at least once for PA," commented William F. Young Jr., MD, professor and chair of endocrinology at the Mayo Clinic in Rochester, Minn. "Diagnosis of PA provides clinicians with a unique opportunity in medicine, to provide either surgical cure or targeted pharmacotherapy. It's been frustrating to me to see patients not tested for PA when first diagnosed with hypertension, but only after they developed irreversible chronic kidney disease," he said in an interview. Dr. Young cited statistics that only about 2% of patients diagnosed with treatment-resistant hypertension are assessed for PA, and only about 3% of patients with hypertension and concomitant hyperkalemia. "Primary care physicians don't think about PA and don't test for PA," he lamented.

The new study "is very convincing, and confirms and extends the findings of several other groups that previously reported the high prevalence of PA among patients with hypertension," commented Dr. Stowasser. Despite this accumulating evidence, uptake of testing for PA, usually starting with spot measurement of renin and aldosterone to obtain an ARR, has "remained dismally low" among primary care and specialist physicians in Australia, the United States, Europe, and elsewhere, he added.

One stumbling block may be the complexity, or at least perceived complexity, of screening by an ARR and follow-up steps as recommended in a 2016 guideline issued by the Endocrine Society and endorsed by several international medical societies including the American Heart Association, Dr. Carey said. Dr. Funder chaired the task force that wrote the 2016 Endocrine Society PA guideline, and the eight-member task force included Dr. Carey, Dr. Stowasser, and Dr. Young.

The new study highlights what its authors cited as a limitation of the ARR for screening. When set at the frequently used ratio threshold of 30 ng/dL/ng/mL per hour to identify likely cases of PA, the crude PA prevalence rates corresponding to this threshold were 4% in treated stage 1 hypertensives, 10% in treated stage 2 patients, and 7% in those with resistant hypertension, substantially below the adjusted PA prevalence rates calculated by applying different criteria for excess aldosterone. In addition to missing clinically meaningful cases, the ARR may also underachieve at a functional level, Dr. Carey suggested.

"We note the difficulty with point assessment of ARR, but that's what we have at the moment. We'll look for other ways to identify patients with excessive aldosterone production," he said. "We need to design a [diagnostic] pathway that's easily doable by primary care physicians. Right now it's pretty complicated. Part of the reason why primary care physicians often don't screen for PA is the pathway is too complicated. We need to simplify it."

In his editorial, Dr. Funder wrote that "much of the present guideline needs to be jettisoned, and radically reconstructed recommendations should be developed."

One answer may be to apply a less stringent ARR threshold for further work-up. Dr. Stowasser's program in Brisbane, as well as some other groups worldwide, use an ARR of at least 20 ng/dL as an indication of possible PA. "If you lower the cutoff to 20 [ng/dL], and ignore the plasma aldosterone level, then the ARR should pick up the great majority of patients with PA," he said.

Another controversial aspect is whether aldosterone detection should be screened by 24-hour urine collection or by spot testing. In his editorial, Dr. Funder called spot testing "useless" and "misleading," but Dr. Vaidya acknowledged that the 24-hour collection used in his current study is "not practical" for widespread use. Despite that, the Mayo Clinic in Rochester has focused on 24-hour urine collected "for more than 4 decades," said Dr. Young, even though "a morning blood sample remains a simple screening test" that will catch "more than 95% of patients with PA" when combined with a plasma aldosterone threshold of 10 ng/dL. Dr. Stowasser noted that "patients don't like" 24-hour collection, and not infrequently muck up collection” by forgetting to collect their entire 1-day output. Regardless of its shortcomings, 24-hour urine has the advantage of greater precision and accuracy than spot measurement, and using it on newly diagnosed hypertensive patients who also show renin suppression may be a viable approach, Dr. Carey suggested.

Regardless of exactly how guidelines for assessing aldosterone in hypertensive patients change, prospects seem ripe for some sort of revision and for greater participation and buy-in by primary care physicians than in the past. Dr. Carey, who also served as vice-chair of the American College of Cardiology and American Heart Association Task Force that wrote the most current U.S. guideline for managing hypertension, said it was too soon to revise that document, but the time had come to revise the Endocrine Society's 2016 guideline for diagnosing and treating PA and to hash out the revision "in partnership" with one or more primary care societies. He also highlighted that publishing the current study in a high-profile primary care journal was an intentional effort to reach a large segment of the primary care community.

The new report "has the potential to change the current state of inertia" over wider PA diagnosis and targeted treatment "by being published in a widely read, major international journal," commented Dr. Stowasser.

Dr. Vaidya has been a consultant to Catalys Pacific, Corcept Therapeutics, HRA Pharma, Orphagen, and Selenity Therapeutics. None of the other report coauthors had commercial disclosures, including Dr. Carey. Dr. Funder, Dr. Stowasser, and Dr. Young had no disclosures.

mzoler@mdedge.com

SOURCE: Brown JM et al. Ann Int Med. 2020 May 25. doi: 10.7326/M20-0065.

This article originally appeared on MDedge.com.

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