Non-invasive wearable patch could monitor oestrogen in sweat

Researchers from the California Institute of Technology have developed a wearable sensor that could reliably monitor estradiol by detecting its presence in sweat.

The sex hormone commonly known as oestrogen plays an important role in multiple aspects of women’s health and fertility.

High levels of oestrogen in the body are associated with breast and ovarian cancers, while low levels of estradiol can result in osteoporosis, heart disease, and even depression.

Oestrogen is a class of hormones that includes estradiol as the most potent form. Estradiol is also necessary for the development of secondary sexual characteristics in women and regulates the reproductive cycle.

Because of its many functions, estradiol is often specifically monitored by doctors, but this usually requires the patient to visit a clinic to have blood drawn for analysis in a lab.

The new wearable sensor, scientists argue, could monitor estradiol by detecting its presence in sweat, making it easier for women to monitor their estradiol levels at home and in real time.

The research, published in Nature Nanotechnology, was conducted in the lab of Wei Gao, assistant professor of medical engineering, investigator with the Heritage Medical Research Institute, and Ronald and JoAnne Willens Scholar.

Gao has previously developed sweat sensors that detect cortisol, the presence of the COVID-19 virus and a whole slew of other nutrients and biological compounds.

He says the development of the estradiol sensor was spurred in part by requests from people who were unsatisfied with the options they had for monitoring their oestrogen levels.

“People often ask me if I could make the same kind of sweat sensor for female hormones, because we know how much those hormones impact women’s health,” he explains.

The primary challenge, and what dictated changes in the sensor’s design, is that estradiol, which already is present at fairly low levels in the blood, is roughly 50 times less concentrated in sweat.

“Since it’s such a low concentration, it’s very challenging to detect estradiol automatically in sweat,” Gao says.

Despite this, testing in the laboratory has shown that the sensor could reliably and accurately track the changing levels of estradiol in sweat over the course of the reproductive cycle, from the lowest level during menstruation to its highest level (10 times greater) during ovulation.

Who could benefit from estradiol monitoring?

One population of women who could benefit from estradiol monitoring are those who are attempting to conceive, either naturally or through IVF.

The success of either method, Gao says, is dependent on getting timing right with regards to ovulation, but not all women have a reproductive cycle that follows a regular schedule.

Some women have been able to track their ovulation by monitoring their body temperature, but the researcher points out that method has limited usefulness because it is not very accurate and body temperature does not increase until ovulation has begun.

He says: “Because oestrogen increases before ovulation, with this sweat sensor, we would be able to give people notice ahead of time.”

Women undergoing hormone replacement therapy (HRT) could also benefit from a wearable oestrogen sensor, Gao adds, as their bodies do not produce sufficient estradiol.

In these patients, however, estradiol levels will need to be carefully monitored to ensure they are taking the correct dosage.

Gao says he plans to continue working on this technology to allow it to monitor other female hormones, like luteinising hormone or progesterone, which are both involved in ovulation.

He and his team hope to “miniaturise” the sensors so they could all fit inside of small wearable devices.