1694-P: Expression of GLP-1R and GIPR in Papillary and Medullary Thyroid Carcinoma and Hashimoto’s Thyroiditis: An Immunohistochemistry H-score Study

Introduction and Objective: Incretin receptor (GLP-1R and GIPR) expression in thyroid pathology is clinically relevant given expanding use of incretin-based therapies. This study assessed GLP-1R and GIPR expression in papillary thyroid carcinoma (PTC), medullary thyroid carcinoma (MTC), Hashimoto’s thyroiditis (HT), and non-neoplastic thyroid tissue. Methods: Twenty-nine thyroid tissue samples were analyzed: PTC (n=9), MTC (n=4), HT (n=8), and non-neoplastic adjacent thyroid tissue from PTC cases (n=8). Immunohistochemistry was performed using pancreatic tissue as positive control; receptor expression was semi-quantified with H-score (0-300). Group comparisons used ANOVA with Bonferroni post-hoc testing. Results: GLP-1R showed strong, homogeneous overexpression in MTC (mean H-score 300/300) versus low-to-moderate, heterogeneous expression in PTC (60.0), HT (57.1), and non-neoplastic tissue (131.4), with significant between-group differences (p<0.001) and MTC higher than all other groups. GIPR demonstrated low-to-intermediate expression (mean values 3.1-60.0) without significant differences among groups (p=0.122), although a trend toward higher expression in MTC was observed (Figure). Conclusion: Marked GLP-1R overexpression in MTC suggests potential diagnostic and biological relevance, whereas GIPR did not significantly discriminate across thyroid conditions studied. Disclosure P. Rakitzi: None. K. Hatzopoulos: None. E. Manthou: None. T. Koufakis: Speaker's Bureau; Current; Novo Nordisk, Lilly, Menarini Group. Advisory Panel; Current; Roche Diabetes Care. Speaker's Bureau; Current; AstraZeneca, Boehringer Ingelheim International GmbH.