By admin 
Primary aldosteronism represents a critical area of focus within hypertension research, not only due to its prevalence but also because it is one of the few potentially curable forms of high blood pressure. Unlike essential hypertension, which has no identifiable cause, PA stems from a specific abnormality in the adrenal glands. These small, triangular glands, perched atop the kidneys, are responsible for producing a range of hormones, including aldosterone, which plays a crucial role in regulating the body’s salt and water balance, and consequently, blood pressure. When aldosterone is excessively produced, it leads to increased sodium retention and potassium excretion, resulting in elevated blood pressure, fluid overload, and damage to the heart and blood vessels over time. The persistent strain on the cardiovascular system explains the heightened risks of heart attack, stroke, kidney disease, and even metabolic disturbances like type 2 diabetes, often observed in patients with PA.
The challenge with diagnosing primary aldosteronism lies in the inherent variability of hormone secretion and the limitations of conventional diagnostic methods. Historically, the diagnosis of PA has been complex, requiring a multi-step process that often begins with screening tests such as the plasma aldosterone concentration to plasma renin activity ratio (PAC/PRA). If this ratio is elevated, patients typically undergo confirmatory tests like saline infusion tests, oral salt loading tests, or fludrocortisone suppression tests, all of which require specific preparation, dietary restrictions, and often, hospital visits. These tests aim to determine if aldosterone secretion is autonomously high, meaning it is not suppressed by normal physiological mechanisms. Further localization of the problem—whether it affects one adrenal gland (unilateral PA) or both (bilateral PA)—often necessitates adrenal vein sampling (AVS), an invasive and technically demanding procedure requiring specialized expertise, which is not widely available.
One of the most significant hurdles identified by the recent research is the dynamic nature of aldosterone production. Researchers from a collaborative team spanning the University of Bristol and the University of Manchester in the UK, the University of Bergen in Norway, and partners in Stockholm and Athens, discovered that individuals with primary aldosteronism do not exhibit a constant, uniformly elevated level of aldosterone. Instead, their hormone production can manifest in unpredictable bursts, occurring both during the active hours of the day and, crucially, while they are asleep at night. These nocturnal surges are particularly problematic for diagnosis, as routine blood tests are almost exclusively performed during daytime hours, invariably missing these critical nighttime fluctuations. This inherent variability means that a single blood test, taken at a particular moment, could easily capture a period when hormone levels appear relatively normal, leading to a false negative and a missed diagnosis.
To overcome these diagnostic blind spots, the research team employed an innovative portable device developed at the University of Bristol. This groundbreaking technology allowed patients to have their hormone levels continuously monitored in their natural home environment, rather than being confined to a hospital ward or research facility. This shift from static, point-in-time measurements to dynamic, continuous monitoring represents a potential revolution in endocrinological diagnostics. The device, known as U-RHYTHM, is lightweight and compact, roughly the size of a mobile phone, and attaches comfortably at the waist. Its ingenious design allows it to sample hormones directly from the skin, a non-invasive method that eliminates the need for repeated blood draws or intravenous access. This enabled participants to maintain their normal daily routines, including sleeping, while the device meticulously collected detailed hormone data every 20 minutes over a 24-hour period. The technology’s potential was recognized quickly, leading to its adoption and further development by the spin-out company Dynamic Therapeutics in 2023, signaling its readiness for broader clinical application.
The proof-of-concept study involved 60 patients across the participating cities of Bristol, Bergen, Stockholm, and Athens. The continuous data stream revealed a previously hidden pattern of nocturnal hormone bursts, fundamentally altering the understanding of primary aldosteronism. Dr. Eder Zavala, UKRI Future Leader Fellow at the University of Manchester and a senior author of the study, emphasized the significance of this discovery: "By continuously monitoring hormones over 24 hours, we were able to reveal a previously hidden pattern of nocturnal hormone bursts. This gives us a much clearer understanding of the disease and could ultimately help doctors detect it earlier and treat patients more effectively." This deeper insight into the disease’s temporal dynamics suggests that a more detailed mathematical and computational analysis of daily hormonal profiles could even help uncover earlier and more subtle forms of the disease, paving the way for improved patient outcomes.
The researchers used advanced computational analysis to track the fluctuations of aldosterone, alongside two closely related hormones, 18-hydroxycortisol and 18-oxocortisol, which are precursors in the aldosterone synthesis pathway and can also be elevated in PA. The findings unequivocally demonstrated that aldosterone levels do not remain consistently elevated, often dropping below the minimum thresholds typically used for diagnosis, even in some of the most severe cases. Instead, aldosterone showed repeated, distinct bursts of secretion at night, while the overall day-night rhythm of hormone activity paradoxically remained intact. This means the body still maintains a general diurnal pattern, but the manner of hormone release is profoundly altered, characterized by these irregular, powerful surges.
Importantly, these hormone spikes were found to originate from the adrenal glands themselves and were particularly pronounced in patients whose primary aldosteronism was caused by a problem affecting only one adrenal gland (unilateral PA), rather than both. The compelling evidence came when these unusual hormone patterns disappeared entirely after the affected adrenal gland was surgically removed. This direct correlation provided strong, undeniable proof that the observed bursts were intrinsically linked to the disease process, confirming their diagnostic significance.
These revelations carry profound implications for the future of diagnosing primary aldosteronism. Professor Stafford Lightman, Professor of Medicine at the University of Bristol and the inventor of the U-RHYTHM technology, stated, "The findings suggest that clinicians may need to rethink how they look for the disorder, which the Endocrine Society clinical practice guidelines now recommend should be considered for all people with hypertension, also known as high blood pressure." This recommendation, made by a leading international endocrine body, underscores the growing recognition of PA’s importance. However, its widespread implementation has been hindered by the very diagnostic challenges this new technology aims to address.
Dr. Thomas Upton, Clinical Research Fellow at the University of Bristol and co-lead author, highlighted the current difficulties: "Primary aldosteronism is an important cause of high blood pressure and the most common cause of secondary hypertension we see in our blood pressure clinic. It could be affecting millions of people in the UK. However, due to the way hormones change during the day and the current complexity of the diagnostic process, diagnosis is often delayed or never made at all." He further added, "In our study, patients were monitored at home during normal activity, and this allowed us to see how hormones changed over time in realistic settings. This approach could potentially revolutionize how we diagnose hypertension and ultimately reduce cardiovascular disease – particularly heart disease and strokes – that could have been prevented."
The findings strongly advocate for a paradigm shift in diagnostic approaches, moving away from reliance on single, static blood tests towards tracking the body’s hormone rhythms over extended periods, especially focusing on the overnight patterns that appear to hold crucial clues to the disease. This dynamic measurement could significantly improve the accuracy and timeliness of diagnosis. Because primary aldosteronism is a treatable, and in some cases, curable condition—either through specific mineralocorticoid receptor antagonist medications or, for unilateral cases, surgical removal of the affected adrenal gland (adrenalectomy)—earlier and more accurate detection holds immense potential. It could dramatically reduce the risk of preventable cardiovascular complications, saving lives and improving the quality of life for millions worldwide.
Looking ahead, further research will be essential to define the best clinical pathways for integrating dynamic hormone measurement into routine practice. This includes larger-scale clinical trials, cost-effectiveness analyses, and the development of standardized protocols for interpreting the rich data streams generated by continuous monitoring devices. The potential for this technology extends beyond primary aldosteronism, opening doors for better understanding and diagnosis of other hormone-related conditions characterized by pulsatile or intermittent secretion. The vision is clear: to transition from a reactive, snapshot approach to diagnosis to a proactive, continuous monitoring strategy that captures the full physiological picture, ultimately leading to earlier intervention and better health outcomes for patients with high blood pressure and other endocrine disorders.
This groundbreaking research was made possible through the generous support of various funding bodies, including EU Horizon 2020, the Trond Mohn Foundation, the UKRI Biotechnology and Biological Sciences Research Council (BBSRC), Medical Research Council, University Hospitals Bristol and Weston NHS Foundation, the Swedish Medical Research Council, and the Knut and Alice Wallenberg Foundation. The study also strongly aligns with the University of Bristol’s overarching research ‘Grand Challenge’ focused on Understanding and Preventing Cardiovascular Disease and builds upon existing NIHR-funded initiatives aimed at the earlier identification of individuals at risk of hypertension and other cardiovascular diseases, underscoring its pivotal role in advancing public health.
