Is Hair Loss a Class Effect of GLP-1 Receptor Agonists? A Structured Review of Semaglutide and Related Therapies

Semaglutide and other GLP-1 receptor agonists have risen sharply in clinical use for obesity and metabolic disease, and reports of treatment-associated hair loss have become increasingly visible across dermatology and primary care settings. We aimed to characterize the strength, reproducibility, and consistency of this association using a structured PubMed search and evidence synthesis. Twenty-five records were identified, of which thirteen met inclusion criteria spanning pharmacovigilance disproportionality analyses, retrospective cohorts, randomized controlled trial meta-analysis, case reports, narrative syntheses, and commentary. Across these heterogeneous designs, alopecia repeatedly emerged as a measurable and ranked adverse event signal, particularly within FAERS-based datasets and comparative cutaneous adverse event analyses. Case-level reports and narrative syntheses provided clinical phenotype context, whereas quantitative FAERS analyses demonstrated disproportionate representation of hair loss events among GLP-1 exposed patients. Several publications further suggested that signal strength is not semaglutide-exclusive and may extend to tirzepatide, supporting a potential class-level effect. These converging findings indicate that drug-associated alopecia linked to GLP-1 receptor agonists is unlikely to reflect spurious reporting alone. Dermatologists should incorporate GLP-1 exposure in alopecia evaluation, and prescribing clinicians should proactively counsel patients regarding hair loss risk. Prospective studies are needed to define time-course, molecular basis, risk stratification, reversibility, and management strategies.