GLP-1 Receptor Agonists and Alopecia: A Systematic Review and Meta-Analysis of Incidence, Risk, Subtypes, and Mechanisms.

INTRODUCTION: GLP-1 receptor agonists (GLP-1 RAs) are among the fastest-growing pharmacological classes globally. Alopecia has emerged as a clinically relevant adverse effect signal, yet pooled quantitative estimates of risk by subtype and agent are lacking. The objective of this study was to estimate the pooled risk of alopecia associated with GLP-1 RA use, stratified by subtype, agent, and follow-up duration, and to synthesize mechanistic and management evidence. METHODS: PubMed/MEDLINE, Embase, Cochrane Central, Web of Science, and Scopus were searched from inception to March 31, 2026, with no language restrictions. Studies reporting alopecia outcomes in adult GLP-1 RA users were eligible, including cohort studies, pharmacovigilance disproportionality analyses, and case series (n ≥ 5). Of 1,847 identified records, 17 met eligibility criteria. Random-effects meta-analyses (DerSimonian-Laird) were performed for odds ratios (ORs) and reporting ORs (RORs). The protocol was prospectively registered in PROSPERO (CRD420261335458) and PRISMA 2020 guidelines were followed. RESULTS: Seventeen studies encompassing 1,091,743 patient-exposures were included. The pooled OR for any non-scarring alopecia was 1.40 (95% CI: 1.33-1.48; I 2 = 0%; 3 cohort studies). Significant associations were found for telogen effluvium (aOR, 1.76; 95% CI: 1.34-2.32) and androgenetic alopecia (aOR, 1.64; 95% CI: 1.35-1.99) at 12 months; alopecia areata was not significant (aOR, 1.08; 95% CI: 0.87-1.34). Pharmacovigilance signals were highest for semaglutide (ROR, 2.46; 95% CI: 2.14-2.83) and tirzepatide (ROR, 1.73; 95% CI: 1.43-2.10). Paradoxically, 58% of patients with central centrifugal cicatricial alopecia showed improvement with GLP-1 RA use. CONCLUSION: GLP-1 RAs are associated with a significant 40% increased risk of non-scarring alopecia, driven by telogen effluvium and androgenetic alopecia and primarily mediated by weight loss-induced micronutrient deficiency. Semaglutide and tirzepatide carry the highest pharmacovigilance burden. Dermatologists should counsel patients proactively, optimize nutrition, and avoid premature drug discontinuation.