Association Between Tirzepatide Therapy and Thyroid Function in Euthyroid Patients With Obesity

Abstract

Background: Tirzepatide, a dual glucagon-like peptide-1/glucose-dependent insulinotropic polypeptide receptor agonist, effectively reduces weight and improves metabolic parameters in obesity. Its effects on thyroid function, particularly thyroid-stimulating hormone (TSH) and free thyroxine (fT4), in euthyroid patients are unclear. This study aimed to evaluate changes in thyroid function, along with anthropometric, glycemic, and lipid profiles in euthyroid adults with obesity after 1 month of tirzepatide therapy.

Methods: In this single-center retrospective observational study, 38 euthyroid adults with obesity were evaluated after initiation of tirzepatide therapy. Exclusion criteria included prior thyroid disease or use of medications affecting thyroid function. Baseline and 1-month follow-up measurements included TSH, fT4, and selected metabolic parameters. Statistical analyses were performed using suitable parametric or non-parametric methods for within-group comparisons, with categorical variables analyzed via Chi-square tests. Correlation analyses were conducted to evaluate associations between variables. A P value of less than 0.05 was considered statistically significant.

Results: After 1 month of therapy, body weight, body mass index, fasting blood glucose, low-density lipoprotein, triglycerides, and total cholesterol decreased significantly. TSH decreased and fT4 increased significantly, with both remaining within the euthyroid range.

Conclusions: In this short-term retrospective analysis, tirzepatide therapy in euthyroid adults with obesity was associated with modest but statistically significant changes in TSH and fT4 levels, both of which remained within the established euthyroid reference range. These findings represent early biochemical observations and should be considered hypothesis-generating. Further prospective studies with longer follow-up are required to determine the clinical relevance of these changes.