Among 5,370 Medicare patients taking levothyroxine, starting GLP-1 receptor agonists produced no change in thyroid-stimulating hormone testing patterns compared to SGLT-2 inhibitors, with both groups averaging 130.5 days to testing and 83% receiving tests within one year. This represents a significant clinical oversight. GLP-1 drugs like semaglutide and tirzepatide routinely produce 10-20% weight loss, which substantially reduces levothyroxine requirements since thyroid hormone needs scale with body mass. Excess levothyroxine from unchanged dosing can trigger atrial fibrillation, bone loss, and hyperthyroid symptoms—serious risks in older adults. The finding exposes a dangerous disconnect between prescribing patterns and physiological reality. With over 40 million Americans on levothyroxine and GLP-1 prescriptions surging for obesity treatment, this monitoring gap affects millions. The study's retrospective design and Medicare population limits broader generalizability, but the core issue spans all ages. This confirmatory research quantifies what endocrinologists have suspected: rapid weight loss from newer diabetes drugs requires proactive thyroid monitoring protocols that current clinical practice fails to implement.