STUNNING NEWS: Zepbound Shrinks Breast Tumors in Mice.

Last week at ENDO 2025, we looked at how GLP-1 medications might protect the heart after a heart attack. The study showed that GLP-1 therapy didn’t just help with weight loss. It relaxed the capillaries inside the heart, restored blood flow, and potentially reversed microvascular damage.

Now, another ENDO headline is pushing the boundary even further.

Zepbound just shrank breast cancer tumors in obese mice.

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Researchers at the University of Michigan used a well-established model for obesity-associated breast cancer. Mice were fed a high-fat diet to induce obesity, then implanted with breast cancer tumors in the mammary fat pad. This model mimics the way obesity fuels cancer growth in women. Once the mice were fully obese and tumor-positive, they were given either tirzepatide (Zepbound) or a placebo every other day for 16 weeks.

The results?

• Mice on Zepbound lost about 20 percent of their body weight, mostly from fat.

• Tumor volume dropped significantly alongside that fat loss.

• The less fat remaining in the body, especially in the liver, the smaller the tumors became.

This was not about cosmetic weight loss. It was about shifting the internal chemistry that allows disease to grow.

And yes, this is a preclinical mouse study. It has not yet been peer-reviewed or published in a medical journal. But it was presented at ENDO, one of the top endocrine conferences in the world. These are respected researchers doing rigorous work. It’s early, but it’s serious.

This now makes two major studies from ENDO 2025 pointing to something bigger:

• One showed GLP-1s restoring blood flow to the heart after a heart attack by relaxing pericytes and opening up capillaries.

• The other showed GLP-1s shrinking breast tumors in obese mice by altering fat stores and liver metabolism.

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In both cases, the disease process wasn’t just slowed down. It was actively reversed. And in both cases, weight loss alone didn’t fully explain it. These drugs are doing more than moving the needle on the scale. They are reshaping what happens inside the body.

If you are a woman with obesity, this is not just interesting, for many of you it’s personal. If you are a policymaker, employer, or insurer, this should make you take a long look at your current stance on coverage.

GLP-1s are not lifestyle enhancers. They are disease-interrupting tools. And the science is starting to catch up with what patients have known all along.

Zepbound might not just help people live lighter. It might help them live longer.

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