At 2 a.m., while a household sleeps, something in the body may be flaring that every doctor’s office test simply cannot see. Small, noisy bursts of hormone production. Brief. Recurrent. Powerful enough to nudge blood pressure upward over years.
Researchers have now used a waist-worn monitor to catch those bursts in real life. The device, called U-RHYTHM, sampled hormones from the skin every 20 minutes for a full day in 60 patients across Bristol, Bergen, Stockholm and Athens. That uninterrupted record revealed a pattern no single blood draw would have captured: aldosterone—the hormone that controls salt, water and vascular tone—did not sit at a steady high in many patients. Instead it climbed and fell, often spiking at night.
Continuous 24-hour hormone tracking revealed short, repeated aldosterone surges—often at night—that routine clinic tests miss.
This matters because the condition behind those surges, primary aldosteronism, is a potentially curable cause of high blood pressure and may affect a far larger share of people with hypertension than clinicians currently recognise. Untreated, it raises the risk of heart attack, stroke, diabetes and other long-term complications. Yet diagnosis is commonly delayed because conventional testing captures just one moment in a rhythm that is anything but constant.
The wearable U-RHYTHM device, attached to patient’s waist.
The study, published in Science Translational Medicine, went beyond aldosterone. Computational reconstruction of sampling data also tracked two sister steroids, 18-hydroxycortisol and 18-oxocortisol, to build a fuller picture of adrenal output across the day and night. Those reconstructed profiles showed that hormone secretion follows a daily rhythm punctuated by brief surges—noisy signatures that can dip below diagnostic thresholds between peaks. In plain terms: a clinic blood draw taken at the wrong minute can falsely reassure both patient and doctor.
There was another startling clue. When the abnormal hormone storms came from a single adrenal gland rather than both, the nocturnal spikes were especially evident. That distinction is clinically important because unilateral disease can sometimes be cured by removing the affected gland. In the patients who underwent surgery, the bursts disappeared, strengthening the link between the surges and the underlying adrenal pathology.
The wearable U-RHYTHM device, developed by the University of Bristol.
The U-RHYTHM monitor itself is compact, roughly the size of a smartphone, and adheres at the waist to sample hormones through the skin. Developed at the University of Bristol and refined after 2023 by the spinout Dynamic Therapeutics, it enabled monitoring in patients' homes during ordinary daily life instead of under the unnatural constraints of a hospital bed. Real-world data, in other words, not laboratory theatre.
So where does this leave clinical practice? The findings invite a rethink. Current guidelines already urge clinicians to consider primary aldosteronism in people with hypertension, but they still rely heavily on isolated tests. Continuous or repeated monitoring could give clinicians a far richer diagnostic signal, especially by exposing nocturnal activity that is typically invisible.
(left to right) Dr Thomas Upton and Professor Stafford Lightman from the University of Bristol holding the pioneering wearable device, which monitors hormone levels 24/7.
This was a proof-of-concept study, not a new diagnostic protocol. Larger trials will be needed to decide how best to interpret continuous hormone profiles and whether wearable monitoring should become routine. Still, the message is clear: hormones tell a story over time, and listening for a day or more may reveal chapters we have been missing.
Could a simple wearable change the way we hunt for a curable cause of high blood pressure? The evidence is mounting that it can, and that timing—literally the time of day—matters as much as magnitude.
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