THE RAT FINDING
In long-term studies in rats, semaglutide and similar peptides produced tumors in thyroid C-cells (a specific cell type in the thyroid) at clinically relevant exposures.
Whether that finding translates to humans hasn't been established the same way. The boxed warning still applies to the label.
THE CONTRAINDICATION
The FDA's response is a contraindication for a specific subgroup. People with a personal or family history of medullary thyroid carcinoma (a specific kind of thyroid cancer), or with Multiple Endocrine Neoplasia syndrome type 2 (a genetic condition), are advised not to use these peptides.
For everyone outside that subgroup, the human evidence so far doesn't support a population-level cancer claim.
What this means
"Ozempic causes thyroid cancer" overstates what the evidence supports for the general population. The label warning is real and specific. For the people the contraindication applies to, it's binding. For everyone else, the warning is information to know.
Boxed warning came from rats. Human evidence doesn't show a population-level effect.