Functioning glucagonoma associated with primary hyperparathyroidism: Multiple endocrine neoplasia type 1 or incidental association

Diagnosis of multiple endocrine neoplasia type 1 (MEN1) is commonly based on clinical criteria, and confirmed by genetic testing. In patients without known MEN1-related germline mutations, the possibility of a casual association between two or more endocrine tumors cannot be excluded and subsequent management may be difficult to plan.