Caltech sweat patch tracks two fertility hormones — SkimNews
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- Wei Gao at the California Institute of Technology and colleagues developed a wearable patch that measures both oestradiol and progesterone in sweat, extending their 2023 oestradiol-only prototype.
- The patch uses a mild electrical current to induce sweating, contains DNA molecules engineered to bind each hormone, and transmits estimated levels to a smartphone app via distinct electrical signals.
- A dried buffer on the sensor rehydrates with sweat to standardize pH and salt concentration, addressing the long-standing problem that sweat composition varies between people and over time.
- In a study of nine women spanning reproductive and postmenopausal stages, patch readings closely matched blood tests, with correlations of 0.83 for oestradiol and 0.93 for progesterone (1.0 = perfect match).
- A 28-day trial on three women across reproductive, perimenopausal, and postmenopausal stages showed hormone trajectories on the patch matching expected patterns for each life stage.
- Gillian Goddard at NYU Grossman School of Medicine, who was not involved in the research, said the patch 'has the potential to be less invasive than blood tests and sonograms' and to provide more useful information than current wearables.
- The readings require roughly 9 microlitres of sweat and 90 minutes per measurement; Gao's team next plans larger trials, comparison against urine-based ovulation tests, and checks that the patch predicts ovulation early enough to be actionable.
Why it matters: Current consumer fertility trackers lean on post-ovulation temperature shifts, while accurate hormone monitoring requires blood draws, urine strips, or transvaginal ultrasound at a clinic. A patch that matches blood-test correlations (0.83–0.93) and runs from home could shift hormone tracking from episodic clinical snapshots to continuous personal data — if larger trials confirm the early-sample results.
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