Wearable Hormone Monitor Uncovers a Hidden Cause of High Blood Pressure

A hormone disorder called primary aldosteronism, which may affect up to one in five people with high blood pressure, can be easily missed by routine blood tests, a new proof-of-concept study in Science Translational Medicine has found. The condition raises the risk of heart disease, stroke, diabetes and other serious problems. Researchers from the University of Bristol and Manchester in the UK, the University of Bergen in Norway, and collaborators in Stockholm and Athens found that patients can have hormone bursts both by day and while asleep — and the nighttime surges matter most, since routine blood tests are rarely taken during sleep.

To catch these hidden changes, the team used a Bristol-developed wearable called U-RHYTHM, which measured hormone levels every 20 minutes over 24 hours in 60 patients across the four cities. The lightweight device, about the size of a mobile phone, attaches at the waist and samples hormones through the skin, letting people continue normal activities, including sleep, while data was collected. The technology has been further developed since 2023 by the spinout company Dynamic Therapeutics.

The researchers tracked aldosterone, which helps control the body's salt and water balance, along with two related hormones. Aldosterone did not stay consistently high; even in severe cases, levels sometimes fell below the thresholds normally used for diagnosis, so a single blood test could catch a misleadingly normal moment. Instead, it showed repeated nighttime bursts from the adrenal glands, especially in patients whose condition came from a problem in just one gland — and the unusual pattern disappeared once that gland was surgically removed.

Dr. Thomas Upton of the University of Bristol, the study's co-lead author, said primary aldosteronism is the most common cause of secondary hypertension seen in blood pressure clinics and could be affecting millions of people in the UK, though diagnosis is often delayed or missed. Prof Stafford Lightman, a co-author and inventor of U-RHYTHM, said clinicians may need to move from single-time-point blood tests toward tracking hormone rhythms over time, particularly overnight, though further research is needed.