Diabetes Obes MetabSide Effects & SafetyMeta-AnalysisNovember 25, 2025

Assessment of thyroid cancer risk associated with glucagon-like peptide 1 receptor agonist use.

Vilsbøll T, Stellfeld M, Aroda VR, Dandanell S, David JP, Kristiansen CTP, Rasmussen S, Roberts FL, Hegedüs L

Key Finding

Massive analysis of 101,732 people taking GLP-1 drugs like Ozempic and Victoza found no increased thyroid cancer risk, with only 1 case per 10,000 patient-years reported in real-world surveillance.

What This Study Found

Think of this study as a detective investigation examining whether GLP-1 drugs (like semaglutide/Ozempic and liraglutide/Victoza) increase thyroid cancer risk. The researchers cast an incredibly wide net - analyzing 93 clinical trials with over 100,000 people, plus real-world data from insurance databases and post-marketing reports. Imagine you're looking for a needle in a haystack, but the haystack is enormous and you have multiple teams searching. The clinical trials showed slightly more thyroid cancers in GLP-1 users (like finding 17 needles instead of 10), but this could easily be random chance - like getting heads on a coin flip more often in a small sample. The real-world data told a different story entirely, showing actually fewer thyroid cancers in GLP-1 users compared to people taking SGLT-2 inhibitors (another diabetes drug class). Post-marketing surveillance - which is like having millions of people report any problems they notice - found an incredibly low rate of just 1 thyroid cancer case per 10,000 patient-years of exposure.

Statistics Decoded

HR 1.70 (95% CI 0.99, 3.03) for GLP-1 vs placebo means there might be 70% more thyroid cancers, but we're only 95% confident the real number is somewhere between 'actually 1% fewer' and 'three times more' - basically, we can't tell if there's really any increase. HR 0.87 (95% CI 0.58, 1.29) in real-world data means 13% fewer thyroid cancers in GLP-1 users vs SGLT-2 inhibitor users, but again the range includes 'no difference.' The 0.001 cases per 100 patient-years means if you followed 10,000 people taking these drugs for a year, you'd expect to see only 1 thyroid cancer case - extraordinarily rare.

Why This Matters

This should reassure the millions of people using GLP-1 drugs for diabetes and weight loss that thyroid cancer isn't a realistic concern, with massive real-world evidence showing no increased risk despite early theoretical worries from animal studies.

Original Abstract

Published literature has raised concerns regarding a causal association between glucagon-like peptide 1 receptor agonist (GLP-1RA) use and thyroid cancer risk in adults. In this analysis, we evaluated the association between thyroid cancer risk and GLP-1RA use. Our evaluation included data from (i) 93 liraglutide or semaglutide phase 2 and 3 clinical trials, of which six were cardiovascular outcome trials (CVOTs); (ii) post-marketing surveillance from the Novo Nordisk safety database (evaluating data for liraglutide and semaglutide); and (iii) the US Merative™ MarketScan® Commercial Database. Hazard ratios (HRs) were estimated for overall thyroid cancer risk for treatment groups in the clinical trials and for individuals with type 2 diabetes treated with any GLP-1RAs versus sodium-glucose cotransporter-2 inhibitors (SGLT2is) for the real-world data. Data from all clinical trials across 101 732 participants (totalling 206 950 patient-years of exposure [PYE]) reported low numbers of thyroid cancer events; across all trials, HRs were 1.70 (95% confidence interval [CI] 0.99, 3.03) and 1.83 (0.70, 6.71) for pooled GLP-1RA versus pooled placebo and active comparator, respectively. For CVOTs, the HR (95% CI) for pooled GLP-1RA versus pooled placebo was 1.41 (0.72, 2.81). Post-marketing surveillance data showed a low thyroid cancer reporting rate of 0.001 cases/100 PYE and did not support an association between liraglutide or semaglutide exposure and the number of thyroid cancer events. Analysis of the US Merative™ MarketScan® Commercial Database reported an HR of 0.87 (95% CI 0.58, 1.29) for the occurrence of thyroid cancer in individuals using any GLP-1RAs versus SGLT2is. The totality of data analysed did not suggest an association between liraglutide or semaglutide use and thyroid cancer risk in adults.