Shao, Hui

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.

Abstract Disclosure: N.M. Singh Ospina: None. Y. Chen: None. F. Du: None. J.P. Brito: None. H. Shao: None. Q. Liu: None. R.G. McCoy: None. T. Jiao: None. Background: The levothyroxine dose for patients with hypothyroidism is highly correlated with weight. In patients with hypothyroidism, TSH measurements are used to assess the adequacy of levothyroxine dosing.Since type 2 diabetes (T2D) and obesity are two common comorbidities for patients with hypothyroidism, and the significant weight loss associated with Glucagon-Like Peptide-1 Receptor Agonists (GLP-1 RAs) therapy, the initiation of GLP-1 RA on levothyroxine users may significant increase the need for levothyroxine dose reduction potentially requiring additional TSH tests to assure control. Objectives: To evaluate the timing and frequency of TSH testing within one year of initiation of GLP-1, or sodium-glucose co-transporter 2 (SGLT-2) inhibitors, in patients with T2D on levothyroxine treatment. Methods: We identified a cohort of T2D patients using 15% of Medicare fee-for-service claims data from 2005 to 2020. Cohort entry was defined by the initiation of GLP-1 or SGLT2. Patients needed to continuously receive the same dose of levothyroxine for >6 months and have at least 1 TSH measurement before the index date. We excluded patients with hyperthyroidism, thyroid cancer, end-stage renal disease, HIV/AIDs, organ transplant, or who received medications that affect thyroid levels before the index date. The primary outcome was the timing and frequency of TSH testing within one year after GLP-1 RA initiation. Demographics, comorbidities, and medication use were balanced using 1:1 propensity score matching based on the index date. Results: After matching, no significant demographic differences were observed among the 2,107 patients in GLP-1 RA and SGLT-2 groups, respectively. Overall, 32.1%, 32.3%, and 35.6% were aged 65-70, 70-74, and over 75, with 69.3% female and 87.9% white. In the year before the index date, the average number of TSH tests was higher in the GLP-1 RA (1.16 ± 1.27) compared to the SGLT2 (1.07 ± 1.18, p-value: 0.001). In the year after the index date, the average number of TSH tests declined to 0.93 ± 1.18 for GLP-1 and 0.89 ± 1.13 for SGLT2 (p-value: 0.03). Most patients (48.6 vs. 49.5%) had no TSH tests, 41.3 vs. 40.6% had 1-2 tests, and 10.1 vs. 9.9% had more than 2 tests in the GLP-1 RA and SGLT-2 group, respectively. Fewer patients (32.3 vs. 33.6%) were tested within 0-6 months while the majority (67.7 vs. 66.5%) waited longer than 6 months. The relative risk of TSH testing between the GLP-1 RA group and the SGLT2 group was 1.03 (95% CI: 0.98 to 1.08) 1-year before the index date and 1.00 (95% CI: 0.94 to 1.06) 1-year after the index date. Conclusions: Despite the potential impact of GLP-1 RA on levothyroxine dosing, on average, half of patients did not receive a TSH test after treatment initiation. There were no significant differences in TSH testing patterns between GLP-1 and SGLT2 groups, with similar test frequencies and timing observed. Presentation: Saturday, July 12, 2025

Importance The increasing use of glucagon-like peptide-1 receptor agonists (GLP-1RA) demands a better understanding of their association with thyroid cancer. Objective To estimate the risk of incident thyroid cancer among adults with type 2 diabetes being treated with GLP-1RA vs other common glucose-lowering medications. Design, Setting, and Participants This was a prespecified secondary analysis of a target trial emulation of a comparative effectiveness study using claims data for enrollees in commercial, Medicare Advantage, and Medicare fee-for-service plans across the US. Eligible participants were adults with type 2 diabetes at moderate risk for cardiovascular disease and without history of thyroid cancer who had newly filled prescriptions for GLP-1RA, sodium-glucose cotransporter 2 inhibitor (SGLT2i), dipeptidyl peptidase-4 inhibitor (DPP4i), or sulfonylurea from January 1, 2014, to December 31, 2021. Data were analyzed February 1 to October 31, 2024. Main Outcomes and Measures Overall and piecewise (<1, 1-2, and ≥2 years since treatment initiation) hazard ratios (HRs) for thyroid cancer with use of GLP-1RA vs the other 3 drug classes were estimated using inverse propensity score weighted Cox proportional hazards models. Modified intention-to-treat (mITT) (primary) and as-treated (sensitivity) analyses were performed. Results Of 351 913 patients (mean [SD] age, 65.3 [8.5] years; 173 391 [49.3%] females and 178 522 [50.7%] males), 41 112 started treatment with GLP-1RA; 76 093, with DPP4i; 43 499, with SGLT2i; and 191 209, with sulfonylurea therapy. The numbers of patients diagnosed with thyroid cancer were 69 (0.17%) in the GLP-1RA group, 172 (0.23%) in the DPP4i group, 72 (0.17%) in the SGLT2i group, and 381 (0.20%) in the sulfonylurea group. In the mITT analysis, GLP-1RA initiation was not significantly associated with increased overall risk for thyroid cancer compared to the other 3 diabetes drugs (HR, 1.24; 95% CI, 0.88-1.76). However, the risk for thyroid cancer was significantly higher within the first year after GLP-1RA initiation (HR, 1.85; 95% CI, 1.11-3.08) and was amplified in the overall as-treated analysis that censored patients when therapy was discontinued or another medication was added (HR, 2.07; 95% CI, 1.10-3.95). Conclusions and Relevance This secondary analysis of a target trial emulation of a comparative effectiveness study found that despite the low absolute risk of thyroid cancer among patients receiving GLP-1RA therapy, there was an increased risk of new thyroid cancer diagnoses within the first year of GLP-1RA initiation compared to 3 other diabetes drugs. This finding may have been due to enhanced early detection; therefore, further research is necessary to understand the underlying causes of this association.