TH and thyroid cancer: High doses of TH reduce thyroid cancer cell viability, downregulate cyclin D1 expression, and upregulate the key regulator P21, with Annexin V-P1 staining and DNA ladder assays showing its pro-apoptotic effects on papillary and follicular thyroid cancer cells, further confirming its ability to induce apoptosis and reduce thyroid cancer cell viability [178].