Incidental detection of multiple endocrine neoplasia and medullary thyroid carcinoma before starting GLP-1 agonist: A case report

A man, in his 30s, with a history of obesity and hypothyroidism planned to begin taking a new Glucagon-like peptide-1 (GLP-1) agonist for weight loss. As these medications have been associated with C-cell hyperplasia, a calcitonin level was checked as evaluation prior to starting the drug. This returned at 131 pg/mL (upper limit of normal A; p.Cys609Tyr. germline RET mutation, confirming the diagnosis of multiple endocrine neoplasia 2 syndrome. The patient recovered well from treatment. His first-degree relatives also underwent genetic testing. This case represents a surprising diagnosis of familial multiple endocrine neoplasia 2A prior to starting a Glucagon-like peptide-1 agonist.