Scientists have identified a previously hidden pattern of hormone activity that may explain why a common cause of high blood pressure is frequently missed by standard medical tests. The discovery, made using a new wearable monitoring device, could change how doctors diagnose the condition in future.
The research, published in Science Translational Medicine, focused on primary aldosteronism, a hormone disorder that may affect up to one in five people with high blood pressure. The condition is linked to an increased risk of heart disease, stroke, diabetes and other serious health problems, but is often underdiagnosed.
The study was carried out by researchers from the University of Bristol and the University of Manchester in the UK, the University of Bergen in Norway, and collaborators in Stockholm and Athens. They found that patients with primary aldosteronism can experience bursts of hormone production both during the day and while asleep at night. The nighttime surges are particularly significant because routine blood tests are rarely carried out during sleep.
To capture these hidden fluctuations, researchers used a portable device developed at the University of Bristol that allowed patients to have their hormone levels monitored continuously while living normally at home, rather than in a hospital or research facility.
Dr Thomas Upton, Clinical Research Fellow in Automated Sampling at the University of Bristol and Senior Clinical Fellow at Bristol Hospitals NHS Foundation Trust, said primary aldosteronism was the most common cause of secondary hypertension seen in blood pressure clinics and could be affecting millions of people in the UK. He said diagnosis was often delayed or never made because of how hormones change during the day and the complexity of current diagnostic processes.
"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," Dr Upton said. "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 proof-of-concept study followed 60 patients across Bristol, Bergen, Stockholm and Athens over a 24-hour period. Hormone levels were measured every 20 minutes using a lightweight wearable device, about the size of a mobile phone, which attaches at the waist. Because the device samples hormones from the skin, participants were able to continue their usual activities, including sleeping, while detailed hormone data was collected.
The technology, known as U-RHYTHM, was adopted and further developed by the spinout company Dynamic Therapeutics in 2023.
Dr Eder Zavala, UKRI Future Leader Fellow at the University of Manchester and senior author of the study, said continuous monitoring over 24 hours had revealed 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," he said. He added that more detailed mathematical and computational analysis of daily hormonal profiles could eventually help uncover earlier and more subtle forms of the disease.
Researchers used computational analysis to study changes in aldosterone, a hormone that helps regulate salt and water balance in the body, along with two closely related hormones, 18-hydroxycortisol and 18-oxocortisol. The results suggest current diagnostic approaches may miss some patients because aldosterone levels do not remain consistently elevated.
Even in some of the most severe cases, hormone levels sometimes dropped below the minimum thresholds typically used to diagnose primary aldosteronism. This means a single blood test taken at one moment could capture a period when hormone levels appear relatively normal, potentially leading to missed diagnoses.
Instead of remaining constantly high, aldosterone showed repeated bursts of secretion at night, while the overall day-night rhythm of hormone activity remained intact. The hormone spikes originated from the adrenal glands and were especially pronounced in patients whose primary aldosteronism was caused by a problem affecting only one adrenal gland rather than both.
Notably, the unusual hormone patterns disappeared after the affected adrenal gland was surgically removed, providing additional evidence linking the bursts directly to the disease.
Professor Stafford Lightman, Professor of Medicine at the University of Bristol and inventor of the U-RHYTHM technology, said the findings suggested clinicians may need to rethink how they look for the disorder. He noted that Endocrine Society clinical practice guidelines now recommend the condition should be considered for all people with hypertension.
"Future diagnosis could move away from single time point blood tests and towards tracking the body's hormone rhythms over time, particularly the overnight patterns that appear to hold crucial clues to disease," Professor Lightman said. "Further research is needed to define the best clinical pathways, using dynamic hormone measurement, to ensure early diagnosis of this common and potentially curable cause of high blood pressure."
The findings raise the possibility that future testing for primary aldosteronism could rely less on a single blood sample and depend instead on monitoring how hormones change over time. Because the disorder can be treated and, in some cases, potentially cured, earlier detection could help reduce the risk of preventable cardiovascular complications.
The research was funded by EU Horizon 2020, the Trond Mohn Foundation, the UKRI Biotechnology and Biological Sciences Research Council, the Medical Research Council, University Hospitals Bristol and Weston NHS Foundation, the Swedish Medical Research Council and the Knut and Alice Wallenberg Foundation.
The study supports the University of Bristol's research focus on understanding and preventing cardiovascular disease, and builds on NIHR-funded initiatives aimed at earlier identification of people with hypertension and other cardiovascular risk factors.
