Hormone therapy boosts weight loss drug results by 35% in women, study finds

For women struggling with weight gain after menopause, a new study suggests that adding hormone therapy to a popular obesity drug may lead to greater weight loss.

Postmenopausal women lost about 35% more weight when using menopausal hormone therapy alongside tirzepatide — a GLP-1-based, Food and Drug Administration-approved drug for overweight and obesity — compared to those taking the drug alone, according to a Mayo Clinic study.

The findings, published in February in The Lancet Obstetrics, Gynaecology, & Women's Health, highlight a possible new strategy for addressing weight gain after menopause, when hormonal shifts can increase the risk of obesity, cardiovascular disease and type 2 diabetes.

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"This study provides important insights for developing more effective and personalized strategies for managing cardiometabolic risk in postmenopausal women," Dr. Regina Castaneda, the study’s first author, said in a statement. 

Researchers analyzed 120 postmenopausal women with overweight or obesity who took tirzepatide for at least 12 months, including 40 who also used hormone therapy and 80 who did not.

Hormone therapy is commonly used to treat menopause symptoms like hot flashes and night sweats, while tirzepatide helps regulate appetite and blood sugar.

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Women in the hormone therapy group lost an average of 19.2% of their body weight, compared to 14.0% in the non-hormone group — about 35% greater relative weight loss — with more women reaching significant weight-loss thresholds, according to the study.

Despite the results, researchers emphasized that the study was observational and cannot prove cause and effect.

"Because this was not a randomized trial, we cannot say hormone therapy caused additional weight loss," said Dr. Maria Daniela Hurtado Andrade, an endocrinologist at Mayo Clinic and senior author of the study.

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Outside experts agree that the findings must be interpreted cautiously.

"As with all observational studies, we need to interpret this study with a grain of salt," Dr. Gillian Goddard, a board-certified endocrinologist, told Fox News Digital. 

Goddard, who is also an adjunct assistant professor of medicine at the NYU Grossman School of Medicine, noted that the findings show a link, but do not prove that hormone therapy, which usually includes estrogen, directly caused the additional weight loss.

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"There may be important differences between the two groups," she added. "For one thing, the group taking estrogen may be healthier than the groups that didn't take estrogen … Healthier people are more likely to eat a healthy diet and exercise in addition to taking tirzepatide. That could lead to more weight loss." 

Symptom relief from the therapy may have also improved sleep and well-being, making it easier for the group to maintain diet and exercise routines, Hurtado Andrade noted.

Researchers also pointed to a possible biological explanation. Preclinical data suggest estrogen may enhance the appetite-suppressing effects of GLP-1-based medications like tirzepatide, according to the study.

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Goddard said that theory is plausible but unproven.

"The other possibility is that estrogen interacts with tirzepatide in some way that makes it more potent," she said, adding, "We will need randomized studies to get a better handle on that."

As for safety, experts say using the two together appears safe for most women. However, hormone therapy is not recommended for all patients, especially those with a history of certain cancers, blood clots or other underlying health risks, according to the Mayo Clinic.

Researchers say future randomized trials will aim to confirm the findings and explore whether the combination also improves broader cardiometabolic health outcomes, according to the study.

"If confirmed, this work could speed the development and adoption of new, evidence-based strategies to reduce this risk for millions of postmenopausal women navigating this life stage," said Hurtado Andrade.

Fox News Digital has reached out to the study authors for comment.