Human clinical data finds GLP-1 medications do not raise thyroid cancer risk, challenging earlier animal-based warnings amid ongoing lawsuits.
No increased risk of thyroid cancer has been found with injectable glucagon-like peptide-1 receptor agonists, despite earlier safety concerns surrounding these widely used diabetes and weight loss medications. (1✔ ✔Trusted Source
Do GLP-1 Weight-Loss Shots Like
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A report released this month by the Clayman Thyroid Center in Tampa, Florida, indicates that injectable glucagon-like peptide-1 receptor agonists do not raise the likelihood of a thyroid cancer diagnosis and do not speed up the growth of existing thyroid cancer cells.
GLP-1 medications include diabetes drugs such as Ozempic, Mounjaro, Trulicity, and Rybelsus, as well as weight loss treatments like Wegovy and Zepbound. These medications have gained significant popularity in recent years because of their weight loss benefits.
Rising Popularity and Expanding Safety Concerns
As their use has expanded, questions have surfaced regarding the side effects of glucagon-like peptide-1 drugs and whether manufacturers thoroughly evaluated all potential health risks. Concerns have also been raised about whether patients and healthcare professionals were adequately informed about those risks.
Alongside record-breaking sales, reports have emerged describing serious health complications that were not fully detailed on the original drug labels. These include gastrointestinal conditions such as stomach paralysis and non-arteritic anterior ischemic optic neuropathy, a rare yet severe optic nerve injury that can result in permanent blindness.
Product Liability Claims and Thyroid Warning
Manufacturers Novo Nordisk and Eli Lilly are now facing a growing number of lawsuits involving Ozempic, Mounjaro, and Wegovy. The allegations claim that profit motives contributed to insufficient testing and inadequate safety warnings.
Currently, GLP-1 medications carry a boxed warning based on animal research that suggested a possible link to thyroid disease. During preclinical testing, rodents developed C-cell hyperplasia and experienced faster tumor growth after repeated exposure to these drugs.
The new report, led by Dr. Gary L. Clayman and Dr. Rashmi Roy, analyzed human clinical trial data, adverse event reports, and postmarketing surveillance findings. According to the authors, none of this human data showed evidence that medications such as Ozempic or Mounjaro increased the risk of thyroid cancer.
Human Data Vs Rodent Findings
The authors explained that earlier warning signs stemmed from rats and mice reacting more strongly to glucagon-like peptide-1 exposure than human cells do. They also pointed out that some previous human findings suggesting a higher thyroid cancer risk may reflect detection bias, as patients taking these medications often undergo more frequent medical screening compared to those who are not.
“The best available human evidence does not show that glucagon-like peptide-1 receptor agonists cause common thyroid cancers or even have an effect if you have developed a thyroid cancer. The FDA warning specifically addresses a rare type called medullary thyroid carcinoma and is based primarily on rodent studies, not human data” stated Clayman Thyroid Center Hospital for Endocrine Surgery investigators.
Guidance for Patients With Thyroid Conditions
The report advises that individuals with a history of medullary thyroid carcinoma or multiple endocrine neoplasia type 2 should continue to avoid GLP-1 medications. However, people diagnosed with more common forms of thyroid cancer do not need to be concerned about these drugs affecting their condition.
It further states that medications such as Ozempic, Mounjaro, and Wegovy do not require additional thyroid monitoring.
Supporting evidence in the report aligns with findings published in January 2025 by investigators from Mayo Clinic and Yale School of Medicine, which showed that increased thyroid cancer diagnoses observed in earlier reports disappeared after the first year of treatment.
Ongoing Multidistrict Litigation Proceedings
The findings were released at a time of heightened scrutiny surrounding glucagon-like peptide-1 medications, which have resulted in more than 3,000 product liability lawsuits. Most claims center on gastrointestinal injuries such as stomach paralysis, though some also involve allegations of vision loss.
Both the stomach injury and vision loss cases have been consolidated into two separate multidistrict litigations before United States District Judge Karen Marston in the Eastern District of Pennsylvania.
Judge Marston is overseeing coordinated discovery and pretrial proceedings and has indicated plans to select a small number of representative bellwether cases to proceed as early test trials. These trials are intended to show how juries respond to evidence and testimony that may be repeated across thousands of similar cases.
Before the trials move ahead, Judge Marston has directed both parties to resolve key issues that could significantly affect the litigation, including preemption and general causation.
After those matters are addressed, preparation of the first cases for jury review is expected to proceed. Although verdicts in bellwether trials will not directly determine the outcome of other claims, they are likely to influence settlement discussions.
If no settlements are reached following these trials, cases may be returned to their original courts for individual trial scheduling.
Reference:
- Do GLP-1 Weight-Loss Shots Like
Ozempic and Mounjaro Really
Raise Thyroid Cancer Risk? (https://www.thyroidcancer.com/files/GLP1s-Thyroid-Cancer.pdf )
Source-Medindia