GLP-1s are in the clear: a new study finds no link between GLP-1 RAs and thyroid cancer
You’ve probably heard a lot about GLP-1 medication in the news and on social media over the last few years. GLP-1 receptor agonists (GLP-1 RAs) are an important class of medications used to manage type 2 diabetes, but their benefits go way beyond just managing blood sugar. GLP-1 RAs work by mimicking a natural hormone in the body called GLP-1, which helps boost insulin, lower the hormone that raises blood sugar (glucagon), and even curb appetite.
This concern stems from observations in animal studies, which is why many GLP-1 RAs carry a Boxed Warning (the FDA's strongest safety warning) against their use in patients with a personal or family history of MTC or Multiple Endocrine Neoplasia syndrome type 2 (MEN 2).… but there’s good news! The study acknowledges that there is limited long-term data and that there were increases in diagnosis in some of the short-term data.
"A recent large-scale human observational study found no statistically significant association between GLP-1 RA exposure and an increased risk of overall thyroid cancer over its follow-up period."
A closer look at the study behind the news
A major new study, published in “Diabetes Care” on June 4, 2025, was led by an international team of researchers from institutions like the University of Dundee, University of Michigan, Veterans Affairs, Columbia University, UCLA, Johns Hopkins, Yale, and more. The research team was made up of several experts, including Daniel R. Morales, Fan Bu, Benjamin Viernes, Scott L. DuVall, Michael E. Matheny, and Marc A. Suchard, among others. Using a retrospective, active-comparator new-user cohort design, the study brings significant insights into the safety of GLP-1 medications.
How was the study done?
The participants: The study focused on patients with type 2 diabetes mellitus (T2DM) who had previously received metformin therapy and were initiating either a GLP-1 RA or a comparator drug.
The comparators: To ensure a fair comparison, GLP-1 RA users were compared against new users of other common diabetes medications such as sodium-glucose cotransporter 2 inhibitors (SGLT2is), dipeptidyl peptidase 4 inhibitors (DPP-4is), and sulfonylureas (SUs).
The data sources: The researchers utilized extensive international administrative claims and electronic health record databases. *Important note: while international databases were used, only U.S. cohorts passed study diagnostics and were included in the final cited results.
The observations: The primary outcomes observed were the incidence of thyroid tumor and thyroid malignancy.
The methods used: The study employed rigorous methods to adjust for potential confounding factors, including propensity score matching and stratification, and used Cox regression for hazard ratio estimation.
The results are in: No increased risk found
The researchers analyzed data from a vast number of people across several medication groups:
- 460,032 users of GLP-1 receptor agonists (GLP-1 RAs)
- 717,792 users of SGLT2 inhibitors (SGLT2is)
- 2,055,583 users of DPP-4 inhibitors (DPP-4is)
- 1,119,868 users of sulfonylureas (SUs)
Low incidence of thyroid tumors
Among those taking GLP-1 RAs, the rate of thyroid tumors ranged from 0.88 to 1.03 cases per 1,000 person-years—a relatively low number.
No increased risk found
Here’s the key finding: GLP-1 RAs were not associated with a higher risk of thyroid tumors when compared to other common diabetes medications.
The hazard ratios (HRs) tell the story*:
- GLP-1 RA vs. SGLT2i: HR ranged from 0.83 (95% CI 0.57–1.27) to 0.95 (0.85–1.06)
- GLP-1 RA vs. SU: HR ranged from 0.95 (0.75–1.20) to 1.03 (0.87–1.23)
- GLP-1 RA vs. DPP-4i: HR ranged from 0.78 (0.60–1.01) to 0.93 (0.83–1.04)
*Note on HRs: A hazard ratio of 1.0 indicates no difference in risk between the groups. A 95% Confidence Interval (CI) that includes 1.0 suggests the difference is not statistically significant.
Consistency is key
Even when the researchers focused solely on confirmed thyroid malignancies and added a one-year lag (to rule out early bias), the findings held up. That consistency adds even more confidence to the conclusion.
Conclusion
This large-scale study found no increased risk of thyroid tumors in patients with type 2 diabetes who were starting GLP-1 receptor agonists.
That’s good news for both patients and healthcare providers as it adds an extra layer of reassurance when choosing to begin or to continue GLP-1 medications for managing diabetes.
If you have questions or concerns about your medications, be sure to talk with your healthcare provider. They can help you make informed decisions based on the latest research and your individual health needs.
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The information provided in this blog post, including details about GLP-1 receptor agonists and recent research findings, is for general informational and educational purposes only. It is not intended to be, and should not be construed as, medical advice, diagnosis, or treatment.
Always consult with a qualified healthcare provider regarding any questions about a medical condition, a new treatment, or changes to an existing treatment plan. Do not disregard professional medical advice or delay in seeking it because of information you have read on this blog.
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