Wearable device reveals nocturnal hormone patterns missed by standard blood pressure tests

High blood pressure affects roughly one in five people worldwide, but for millions of them, the real culprit goes undetected. A hormone disorder called primary aldosteronism—which can trigger heart disease, stroke, and diabetes—hides behind standard medical testing because it doesn't announce itself consistently. The condition causes the adrenal glands to overproduce aldosterone, the hormone that regulates salt and water balance, but it does so in bursts rather than in a steady, measurable way. Doctors checking a patient's blood at a single moment in time often miss these spikes entirely.

Researchers at the University of Bristol, working with colleagues in Manchester, Bergen, Stockholm, and Athens, set out to catch what conventional testing was missing. They developed a portable device called U-RHYTHM—roughly the size of a mobile phone, worn at the waist—that measures hormone levels continuously from the skin every 20 minutes, around the clock. In a proof-of-concept study published in Science Translational Medicine, they monitored 60 patients over a full 24-hour period while the patients went about their normal lives, including sleeping. The device revealed a pattern that standard blood tests had consistently failed to capture: nocturnal hormone bursts occurring while patients slept.

The findings were striking. Aldosterone levels did not remain elevated all the time. Even in severe cases, hormone concentrations sometimes dipped below the diagnostic thresholds doctors currently use to identify the disease. But when researchers analyzed the continuous data, they found repeated spikes at night—particularly pronounced in patients whose condition stemmed from a problem in a single adrenal gland rather than both. When those affected glands were surgically removed, the abnormal hormone patterns disappeared, confirming that the bursts were directly tied to the disease.

Dr. Thomas Upton, a clinical research fellow at the University of Bristol, noted that primary aldosteronism is the most common cause of secondary hypertension seen in blood pressure clinics, yet diagnosis is often delayed or never made at all. The condition could be affecting millions of people in the UK alone. The wearable device changes that equation by allowing doctors to see how hormones actually behave in real time, in real settings, rather than relying on a single snapshot taken in a hospital or clinic.

The computational analysis of the continuous data revealed patterns in three key hormones: aldosterone itself, along with 18-hydroxycortisol and 18-oxocortisol. These markers, tracked over time rather than measured once, paint a much clearer picture of disease activity. Dr. Eder Zavala, senior author of the study at the University of Manchester, suggested that more detailed mathematical analysis of daily hormone profiles could eventually uncover earlier and subtler forms of the disease, opening new pathways to better outcomes.

The implications reach far beyond diagnosis. If primary aldosteronism can be caught earlier and more reliably, millions of preventable cases of heart disease and stroke could be averted. Current clinical practice guidelines from the Endocrine Society recommend that all people with high blood pressure be screened for the condition, yet underdiagnosis remains widespread. Professor Stafford Lightman, the inventor of the U-RHYTHM technology, suggested that future diagnosis may shift away from single-point blood tests entirely, moving instead toward tracking the body's hormone rhythms over time—particularly the overnight patterns that appear to hold the crucial clues.

The device was developed at the University of Bristol and later adopted and advanced by the spinout company Dynamic Therapeutics in 2023. The research was funded by major grants including EU Horizon 2020 and support from medical research councils across the UK, Sweden, and Norway. The work builds on broader institutional efforts to understand and prevent cardiovascular disease, part of a larger push to identify people at risk earlier in their disease course. What remains ahead is the work of translating this proof of concept into clinical practice—defining the best pathways for using dynamic hormone measurement in routine care, and training clinicians to interpret these new patterns of disease.