Assessing Thyroid Cancer Risk With GLP-1 Therapy

The rapid clinical adoption of GLP-1 receptor agonists for the management of type 2 diabetes and obesity has been accompanied by persistent questions regarding their oncological safety. Although FDA labeling includes a boxed warning for medullary thyroid carcinoma (MTC), clinicians often face challenges in reconciling animal-model data with real-world patient care.

In a recent white paper and subsequent interview, Gary L. Clayman, DMD, MD, FACS, a thyroid surgeon and the founder of Clayman Thyroid Center, examined the current evidence surrounding this controversial link. Clayman emphasized that much of the existing concern stems from a misunderstanding of the data, particularly the biological differences between rodent and human C-cell responses. Furthermore, he addressed the phenomenon of detection bias—where increased medical surveillance of patients on GLP-1 therapy leads to the incidental discovery of pre-existing, indolent nodules—and clarified that there is no evidence suggesting these agents cause or exacerbate the common thyroid cancers that comprise over 95% of cases.

CancerNetwork®: What was the driving factor behind the white paper?

Clayman: It was patient driven. Patients were asking if it was safe to use their GLP-1 therapy with nodular disease and a history of thyroid cancer or concern for thyroid cancer.

A core theme of your review is that increased monitoring leads to the discovery of preexisting, indolent nodules. Can you expand on that?

We’ve done an exhaustive study that’s about to be published; it’s in press. That was a screening of totally asymptomatic women with no known thyroid nodules or thyroid conditions for thyroid cancer. That screening showed 2.4% of women [who] were asymptomatic without known disease have thyroid cancer. The incidence of thyroid cancer amongst women 25 to 50 years of age is even greater than the incidence of breast cancer, which was thought to be the No. 1 malignancy in that age group. That’s the derivation of this. These patients are seeing endocrinologists or primary care physicians, but many endocrinologists are prescribing the GLP-1 therapies, and they’re very adept at screening because of the concern that’s been raised. Many of them are getting ultrasounds, and it’s leading to these diagnoses.

Can you highlight the mechanistic and translational evidence the paper observed, specifically the differentiation between the animal and human studies?

This has only been shown in animals, and it’s only been shown to affect something called the C-cells, which produce medullary thyroid cancer. No other cells or cell type of the thyroid gland are of issue. Even this evidence has never been shown in humans, meaning the studies that have looked at the incidence of thyroid cancer and medullary thyroid cancer in humans with GLP-1 therapy have not shown any effect whatsoever, so there's no human evidence whatsoever. Because of the animal studies, it is contraindicated in those with medullary thyroid cancer or a history of multiple endocrine neoplasia syndrome.

For a patient with a personal history of papillary thyroid cancer who is struggling with obesity-related comorbidities, how do you weigh the metabolic benefits of a GLP-1 against the theoretical oncological concerns?

There are no theoretical oncologic concerns. There is no reason that anyone with a history of thyroid cancer other than medullary thyroid cancer should have any question about the safety of GLP-1 [treatments].

Should a standard family history assessment be sufficient for patients with medullary thyroid cancer, or should clinicians be more proactive with genetic screening prior to GLP-1 initiation?

Anyone with medullary thyroid cancer should be screened for hereditary disease. That’s standard practice. If you have medullary thyroid cancer, you should screen to determine whether it’s a hereditary disease to understand the disease and understand the potential impact upon other family members.

One of the key takeaways from the paper was that GLP-1 therapy does not require additional thyroid monitoring. What evidence did you find that supports this claim?

There is no relationship to GLP-1 therapy in the incidence of thyroid cancer or the incidence of medullary thyroid cancer. There have been no human studies; therefore, there’s no relevance whatsoever.

What do you hope your colleagues take away from the paper and this conversation?

I hope that professional colleagues can understand why the label has been made for medullary thyroid cancer. That is a very—what I would call—soft call, but there’s tremendous safety, and the benefit of the GLP-1 therapy to patients must be considered in light of the lack of evidence of any concern with regards to thyroid malignancy.

Reference

Clayman GL, Roy R. Do GLP-1 weight-loss shots like Ozempic and Mounjaro really raise thyroid cancer risk? The latest facts explained. Published February 2026. Accessed March 11, 2026. https://tinyurl.com/33y9fwxx

For more information about thyroid cancer, visit: www.thyroidcancer.com