Yes. Both semaglutide and tirzepatide carry an FDA black box warning about thyroid C-cell tumors. In rodent studies, these drugs caused thyroid tumors (medullary thyroid carcinoma). It's unknown whether this applies to humans—rodent thyroid biology differs significantly from human. As a precaution, GLP-1 agonists are contraindicated in people with a personal or family history of medullary thyroid carcinoma or Multiple Endocrine Neoplasia syndrome type 2 (MEN 2). If you have thyroid concerns, discuss with your doctor.