GLP-1 agonist drugs like Ozempic do not increase thyroid cancer risk

Glucagon-like peptide-1 (GLP-1) receptor agonists are a class of drugs used to control blood glucose (sugar) levels in people with type 2 diabetes.
Doctors also prescribe them for people with obesity or overweight with related health conditions, to help them lose weight.
Early studies suggested that GLP-1 receptor agonists might increase the risk of thyroid cancer.
Now, a large-scale Scandinavian study has found no significant increase in thyroid cancer risk in those taking GLP-1 receptor agonists compared with those on other treatments for type 2 diabetes.

Glucagon-like peptide-1 receptor (GLP-1) agonists are an effective treatment for controlling blood glucose levels in people with type 2 diabetes, particularly those who do not respond, or stop responding to, first-line treatments, such as metformin.

There are many versions of GLP-1 drugs, including:

They work by increasing the release of insulin — the hormone that controls blood glucose by moving it into cells — and suppressing the release of glucagon, which releases glucose from the liver into the blood.

GLP-1 agonists also improve insulin sensitivity, slow gastric emptying and increase feelings of fullness after eating.

Clinicians also prescribe the drugs for weight loss in people without type 2 diabetes. Both the Food and Drugs Administration (FDA) in the United States and the National Institute for Health and Care Excellence (NICE) in the United Kingdom have approved some GLP-1 agonists for weight loss and weight control in people with obesity and overweight with related health conditions.

Use of GLP-1 agonists has increased greatly since they were first approved. One concern about the medications, however, is that some studies suggest they may increase the risk of thyroid cancer. However, these studies point out that the health benefits of the drugs are likely to outweigh this increased risk.

Now, a large-scale study has found no significant increase in thyroid cancer risk for people with type 2 diabetes on GLP-1 agonists compared with people treated with DPP4 inhibitors, which, the study reports, have no known thyroid cancer risk.

The study appears in The BMJ.

Björn Pasternak, MD, PhD, lead author, and principal researcher at the Department of Medicine, Solna, at Karolinska Institutet in Sweden, explained why the team conducted the the study.

“Many people take these medicines, so it is important to study potential risks associated with them,” he noted in a press release.

“Our study covers a broad group of patients and provides strong support that GLP-1 analogues are not associated with an increased risk of thyroid cancer,” he added.

This large cohort study used data on more than 145,000 people treated with GLP-1 agonists, and almost 292,000 people treated with DPP4 inhibitors from Norway, Sweden and Denmark.

The GLP-1 agonists used were liraglutide (57.3%), followed by semaglutide (32.9%), dulaglutide (4.9%), exenatide (4.1%), and lixisenatide (0.9%).

The researchers followed up participants after a mean of 3.9 years for the GLP-1 group and 5.4 years for the DPP4 group.

They identified cases of thyroid cancer from nationwide cancer registers. In the GLP-1 group, 76 of 145, 410 people developed thyroid cancer, and in the DPP4 group, 184 of 291, 667 developed the disease.

From these data, the researchers worked out that the relative risk was increased by no more than 31% for those on GLP-1 agonists.

Mir Ali, MD, bariatric surgeon and medical director of MemorialCare Surgical Weight Loss Center at Orange Coast Medical Center in Fountain Valley, CA, not involved in this research, explained what this means for people taking GLP-agonists.

He told Medical News Today that:

“The meaning of relative risk is the risk compared to someone not taking the medication — 31% is very low and indicates that the risk of developing thyroid cancer due to this medication is relatively low.”

Nevertheless, “[c]aution still needs to be taken in patients who fall into the category of hereditary thyroid cancers — like multiple endocrine neoplasia syndromes,” he added.

Thyroid cancer is more common in women than in men, but is still a relatively rare form of cancer. The incidence rates are 10.1 cases per 100,000 women and 3.1 per 100,000 men, and mortality rates from thyroid cancer are low and decreasing. Therefore, a slight increase in relative risk means that the likelihood of developing the cancer is still very low.

GLP-1 agonists have other health benefits, alongside controlling blood glucose and weight loss. Studies have shown that they have cardiovascular benefits, particularly in people with obesity.

Other beneficial effects include reducing blood pressure and blood lipid levels, reducing inflammation, and possibly even helping to treat heart failure in people with obesity and type 2 diabetes.

A recent study found that they may also help delay the progression of chronic kidney disease, which often develops in people with type 2 diabetes.

People should be aware that there are common side effects of GLP-1 agonists, but they are mostly mild. The symptoms, which are generally dose-dependent and usually lessen with ongoing treatment, may include:

gastrointestinal symptoms, such as nausea, vomiting, diarrhea and abdominal pain
irritation/inflammation at the injection site.

Ali told MNT that the study should reassure people, since previous concerns about thyroid cancer risk were from animal studies, adding: “I think this study can help reassure patients taking these medications that they are safe and risk of thyroid cancer is very low.”

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