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Thyroid Biology and Disease

MON-445 - Effect of GLP-1 Receptor Agonist Therapy on Levothyroxine Dosing in Patients with Diabetes Mellitus

Monday, June 15, 2026
9:00 AM - 2:00 PM CT

    Late-Breaking Poster Presenter(s)

  • CO

    Cristina Maria Ortiz Malave, MD

    Fellow
    UNIVERSITY OF NEVADA - LAS VEGAS
    Las Vegas, United States

    • Co-Author(s)

  • AS

    Aakansha Singh, MPH

    UNIVERSITY OF NEVADA - LAS VEGAS
    Las Vegas, United States

    • Senior Author/Primary Investigator(s)

  • KI

    Kenneth Izuora, MD, MBA

    Program Director
    University of Nevada Las Vegas, School of Medicine Endocrine Fellowship Program
    Las Vegas, NV, United States



Introduction:
Hypothyroidism, primarily treated with levothyroxine (LT4), is prevalent in patients with type 2 diabetes mellitus (T2DM). GLP-1 receptor agonists, used to treat T2DM, may influence thyroid homeostasis, but impact on LT4 dose requirements remains unclear. This study evaluated changes in LT4 dose after ≥ 6 months and compared these changes between GLP-1 users and non-users.

Methods:
This retrospective cohort study used electronic medical records from outpatient clinics at a tertiary academic center. Adults (≥18 years) with T2DM, hypothyroidism, and stable LT4 dosing for ≥3 months were included and categorized into GLP-1 users and non-users. Demographic and clinical characteristics were summarized using counts and percentages. Within- and between-group analyses were performed using chi-square tests for categorical variables and independent and paired t-tests for continuous variables. Linear regression assessed predictors of change in LT4 dose.

Results:
Of 418 records reviewed, 93 met inclusion criteria (62 GLP-1 users; 31 non-users). No significant change in LT4 dose was observed among GLP-1 users (p=0.160), whereas a significant change was observed among non-users (p=0.041). Between-group comparisons showed significant differences in change in LT4 dose (p=0.014), HbA1c (p=0.003), and body weight (p=0.047). In regression analysis (adj. R²=0.133, p=0.028), change in LT4 dose was significantly associated with GLP-1 use (p=0.050), change in free T4 (p=0.007), and change in BMI (p=0.022).

Conclusion:
GLP-1 RA therapy was associated with differential changes in LT4 dosing. These findings suggest a potential interaction between GLP-1 RA therapy and hypothyroidism treatments, warranting further investigation in larger, prospective studies.

*Unless otherwise noted, all abstracts presented at ENDO must not be released to the press or the public until the date and time of presentation. For oral presentations, the abstracts are embargoed until the session begins. The Endocrine Society reserves the right to lift the embargo on specific abstracts that are selected for promotion prior to or during ENDO.*