Drug Repurposing for Reducing the Size of Benign Thyroid Nodules: A Systematic Review.

CONTEXT: Benign thyroid nodules (BTNs) are highly prevalent, and current treatment options are primarily invasive. There is a need for effective, noninvasive alternatives.

OBJECTIVE

To systematically evaluate the efficacy of repurposed pharmacologic agents in reducing the size of BTNs.

DATA SOURCES: MEDLINE, EMBASE, Cochrane databases, and Scopus were searched from inception to December 18, 2024.

STUDY SELECTION: We included preclinical and clinical studies evaluating repurposed drugs for BTNs in adults. Of 1499 records screened, 20 studies met inclusion criteria: 6 randomized controlled trials (RCTs), 6 prospective cohorts, 3 retrospective observational studies, 3 case reports, 1 cross-sectional study, and 1 preclinical study.

DATA EXTRACTION: Data were extracted independently in duplicate using a standardized form.

DATA SYNTHESIS: Narrative synthesis was conducted due to heterogeneity. Metformin was the most frequently evaluated agent (7 studies), with 5 studies (including 2 RCTs) reporting statistically significant reductions in dominant nodule volume. One prospective study demonstrated a reduction in the maximum nodule diameter, which was not statistically significant, and 1 RCT showed no changes in nodule size after intervention. Statins (4 studies) and somatostatin analogues (4 studies) showed mixed results. Myo-inositol with selenium, herbal formulations, and immune checkpoint inhibitors showed promise in single studies or case reports.

CONCLUSION

Metformin shows the most consistent potential for noninvasive reduction of BTN size, particularly in patients with metabolic comorbidities. However, current evidence is limited and heterogeneous. Further large-scale studies are needed to confirm efficacy and guide clinical use.