Study Finds No Link Between Thryoid Cancer and Ozempic, Mounjaro, Other GLP-1 Medications

There was little difference in thyroid cancer rates among Ozempic and Mounjaro users, compared to those who took Januvia, Onglyza and similar diabetes medications.

Amid the growing popularity of Ozempic, Mounjaro and other new-generation diabetes and weight-loss drugs, there have been lingering concerns about potential side effects users may face, including long-term gastrointestinal problems, pancreatitis, gallbladder disease and potentially cancer. However, a recent study found that there is no evidence that users face an increased risk of thyroid cancer.

Ozempic and Mounjaro are both part of a new class of medications, known as glucagon-like peptide 1 (GLP-1) receptor agonists, which prior studies have suggested may increase the rate of thyroid C cell tumors among rats, leading the FDA to require a prominent warning about the potential risk and counter-indicate use of the medications among individuals with a personal or family history of medullary thyroid carcinoma (MTC).

In a study published last month in The BMJ, Swedish researchers were unable to find any statistically significant thyroid cancer risk among users from Denmark, Norway and Sweden, compared to users of another class of diabetes drugs, known as dipeptidyl peptidase 4 (DPP4) inhibitors, which include drugs like Januvia, Onglyza and Nesin.

GLP-1 Side Effects

Ozempic and Mounjaro were originally approved for treatment of type 2 diabetes, but they have been hailed as breakthrough weight loss treatments, leading to the widespread use by individuals throughout the United States.

Unfortunately, adoption of the drugs has outpaced the ability of independent researchers to complete thorough studies on the potential side effects of GLP-1, and several safety signals have already emerged among users, most notably involving the development of a painful and debilitating stomach paralysis among some users, known as gastroparesis, which has resulted in a number of Ozempic lawsuits and Mounjaro lawsuits being filed against the drug makers, each raising nearly identical allegations that drug makers withheld critical information from consumers and the medical community to increase profits.

To review the potential Mounjaro and Ozempic thyroid cancer risk, researchers in this latest study looked at data on more than 145,000 patients between 2007 through 2021, comparing those who started treatment with GLP-1 RA inhibitors to those who received DPP4 inhibitors.

Patients who took drugs like Januvia and Onglyza experienced 1.33 thyroid cancer events per 10,000 person years, compared to 1.46 events per 10,000 person years among those taking Ozempic, leading researchers to conclude that there is no current evidence of an increased risk linked to GLP-1 RA inhibitors.

“In this cohort study using nationwide data from three countries, GLP1 receptor agonist use was not associated with a substantially increased risk of thyroid cancer over a mean follow-up of 3.9 years,” the researchers concluded. “In absolute terms, this translates to no more than 0.36 excess events per 10 000 person years, which should be interpreted against the background incidence of 1.46 per 10 000 person years in the comparator group in the study population.”

European regulators came to a similar conclusion in October of 2023.

GLP-1 Stomach Paralysis Lawsuits

While the findings may alleviate concerns over thyroid cancer linked to the popular medications, health experts still voice growing concerns over stomach paralysis, intestinal blockages and other potential side effects, as well as a growing number of lawsuits.

Given common questions of fact and law raised in a growing number of complaints brought throughout the federal court system, the U.S. Judicial Panel on Multidistrict Litigation (JPML) decided in February 2024 to centralize all gastroparesis lawsuits involving any GLP-1 medication before U.S. District Judge Gene E.K. Pratter in the U.S. District Court for the Eastern District of Pennsylvania, as part of an MDL, or multidistrict litigation.

As lawyers continue to review and file claims in the coming months, it is widely expected that thousands of  Ozempic lawsuits, Mounjaro lawsuits and other gastroparesis claims will be transferred to the MDL, as nearly 2% of the U.S. population has been prescribed one of the GLP-1 medications, either for diabetes treatment or weight loss.

To help gauge how juries may respond to certain evidence and testimony that will be repeated throughout the litigation, Judge Pratter will likely establish a bellwether process to prepare a small group of lawsuits involving gastroparesis side effects for early trial dates. However, if the parties are unable to negotiate GLP-1 settlements or another resolution for the litigation after the bellwether trials, the Court may later remand each case back to the U.S. District Court where it was originally filed for trial.