Review examines the connection between GLP-1 drugs (semaglutide, tirzepatide) and thyroid cancer, finding that while animal data raised concerns, human evidence does not support a significant increase in thyroid cancer risk.
Rodent risk does not translateHuman thyroid C-cells have far fewer GLP-1 receptors than rodents, and clinical data shows no significant thyroid cancer increase
What the researchers found
Rodent thyroid tumor findings do not appear to translate to humans. Large-scale human data shows no significant increase in thyroid cancer with GLP-1 drug use.
Why it matters
The thyroid cancer warning on GLP-1 drugs concerns millions of patients and clinicians. Clarifying that the rodent risk does not translate to humans provides important reassurance.
The numbers in context
Data covered 2004 through Q1 2024 from FAERS. Reporting odds ratios were calculated for thyroid cancer across weight-loss medication categories.
How the study worked
Review of preclinical thyroid C-cell data, species differences in GLP-1R expression, clinical trial safety data, and pharmacovigilance reports for GLP-1 drugs.
Who was studied
All patients with thyroid cancer reports associated with weight-loss medications in the FDA FAERS database (2004-Q1 2024)
What this study cannot tell us
Thyroid cancer is slow-growing; long-term follow-up (>10 years) is limited. Medullary thyroid cancer is very rare, limiting statistical power. The boxed warning remains appropriate for patients with MTC family history.
How to read the evidence
Moderate evidence: review of species-specific biology and large-scale human safety data, though very long-term follow-up is limited.
When this study was published
Published in 2025. Most current assessment of GLP-1 drug thyroid cancer concerns.
The bigger picture
The disconnect between rodent and human thyroid responses to GLP-1 drugs is one of the best-studied examples of species-specific drug effects. Understanding these differences is critical for evidence-based risk communication to patients.
Questions still open
- Should the FDA thyroid cancer boxed warning be modified based on human evidence?
- Is very long-term (>10 year) GLP-1 drug use associated with any thyroid changes?
- Should routine thyroid monitoring be recommended for GLP-1 drug users?
Common questions
Do GLP-1 drugs cause thyroid cancer?
Should I get my thyroid checked while on semaglutide?
Read the original research
Exploring Connections Between Weight-Loss Medications and Thyroid Cancer: A Look at the FDA Adverse Event Reporting System Database.
Endocrinology, diabetes & metabolism, 8(2), e70038
Citation
Abi Zeid Daou, Christophe; Aboul Hosn, Omar; Ghzayel, Lana; Mourad, Marc. (2025). Exploring Connections Between Weight-Loss Medications and Thyroid Cancer: A Look at the FDA Adverse Event Reporting System Database.. Endocrinology, diabetes & metabolism, 8(2), e70038. https://doi.org/10.1002/edm2.70038