What is the black box warning about thyroid C-cell tumors with GLP-1 medications?

GLP-1 medications carry an FDA-mandated boxed warning—the strongest warning type—about the risk of thyroid C-cell tumors, including medullary thyroid carcinoma (MTC). This warning is based on studies in rodents where GLP-1 medications caused thyroid C-cell tumors. However, it's unclear whether this risk applies to humans, as thyroid C-cells differ between species and no cases have been definitively linked to these medications in human studies.

You should not use GLP-1 medications if you or family members have a history of MTC or if you have Multiple Endocrine Neoplasia syndrome type 2 (MEN 2). Warning signs of thyroid tumors include a lump in the neck, difficulty swallowing, shortness of breath, or persistent hoarseness. If you experience these symptoms, contact your healthcare provider. While the absolute risk appears very low, discuss your personal and family medical history with your provider before starting treatment.