PMID-20203154 – GLP-1RA Rodent Thyroid C-Cell Activation
Knudsen LB et al. "Glucagon-like peptide-1 receptor agonists activate rodent thyroid C-cells causing calcitonin release and C-cell proliferation," Endocrinology, 2010;151(4):1473-1486. doi:10.1210/en.2009-1272
Quick Reference
| Property | Value |
|---|---|
| PMID | 20203154 |
| DOI | 10.1210/en.2009-1272 |
| Year | 2010 |
| Journal | Endocrinology |
| Study Type | Animal in vivo |
| Evidence Level | V |
| Sample | Rodent models (rats and mice); primate (cynomolgus monkey) comparison |
| Peptide(s) Studied | Semaglutide, Tirzepatide (GLP-1RA class) |
Key Findings
- GLP-1RAs (liraglutide, exenatide) caused dose-dependent thyroid C-cell proliferation in rodents
- C-cell hyperplasia progressed to C-cell adenomas and medullary thyroid carcinoma (MTC) in rodents with chronic exposure
- Calcitonin release was significantly elevated in rodent models
- CRITICAL SPECIES DIFFERENCE: Primate thyroid C-cells showed NO proliferative response to GLP-1RAs
- GLP-1 receptor expression is high in rodent thyroid C-cells but very low or absent in human/primate C-cells
- This species-specific difference in GLP-1R expression explains the differential response
- This study is the original basis for the FDA black-box warning on GLP-1RA labels regarding thyroid C-cell tumors
Study Design
Preclinical study combining in vivo rodent experiments (chronic dosing of GLP-1RAs with thyroid histopathology) with cross-species comparison using cynomolgus monkeys. Included dose-response analysis, calcitonin measurements, GLP-1R expression profiling by immunohistochemistry and RT-PCR across species, and long-term carcinogenicity assessment in rodents.
Limitations
- Animal data; direct translation to human risk is uncertain
- The rodent-specific finding has driven a black-box warning that may overstate human risk
- Primate data limited to relatively short-term exposure
- Doses used in rodent studies were often supraphysiological relative to clinical doses
- The study does not address whether chronic human use at therapeutic doses produces any C-cell effects
Clinical Relevance
This is the foundational study behind the GLP-1RA thyroid cancer black-box warning. Understanding it is essential for patient counseling. The key message: rodent C-cell tumors were caused by species-specific GLP-1R expression that does not exist in humans. While the FDA appropriately required the warning based on preclinical data, the subsequent clinical evidence (PMID-41359966, PMID-38018310) shows that the actual human thyroid cancer risk is far lower than predicted from rodent data. Patients can be reassured that the black-box warning reflects regulatory caution from animal data, not confirmed human carcinogenicity. MTC/MEN2 family history remains a contraindication.
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#research #animal-in-vivo #evidence-level-V #cancer