JIAO, TIANZE

Abstract Context Glucagon-like peptide-1 receptor agonists (GLP-1 RAs) are widely prescribed for type 2 diabetes and obesity and can lead to substantial weight loss. In patients taking levothyroxine, weight loss can reduce thyroid hormone requirements and potentially associated adverse effects. Thyroid-stimulating hormone (TSH) monitoring is essential but unclear whether thyroid function is routinely reassessed after GLP-1 RAs initiation. Objective Examine the changes in the timing of TSH testing after GLP-1 RAs. Design Retrospective cohort study emulating a target trial using Medicare from January 1, 2011, to December 31, 2020. The primary analysis followed an intention-to-treat approach. Patients were matched 1:1 using propensity scores. Logistic regression models and informed by least absolute shrinkage operator variable selection were used. Setting The 15% sample of U.S. Medicare fee-for-service claims data. Patients or Other Participants Adults aged ≥65 years with type 2 diabetes on a stable levothyroxine dose at baseline. Intervention(s) Initiation of GLP-1 RAs vs initiation/ongoing use of sodium-glucose cotransporter-2 inhibitors (SGLT-2is). Main Outcome Measure(s) TSH testing during follow-up. Results Among 5370 matched patients, the mean age was 73.2 years. 71.6% were women, and 87.1% were White. Approximately 83.0% of patients in both treatment groups receive a TSH testing within a 1-year follow-up. The mean time to TSH testing was approximately 130.5 days for both groups. Conclusion TSH testing patterns did not differ between GLP-1 RAs and SGLT-2is, despite the greater likelihood of requiring levothyroxine dose adjustment associated with weight loss seen with GLP-1 RA therapy. Given levothyroxine's widespread use, this gap suggests missed opportunities for timely and weight-responsive thyroid monitoring.