Multiple endocrine neoplasia type 1 with concurrent Cushing's disease, prolactinoma, and multifocal pancreatic neuroendocrine tumors including insulinoma: a case report.

BACKGROUND: Multiple Endocrine Neoplasia type 1 (MEN1) is an autosomal dominant tumor predisposition syndrome involving primary hyperparathyroidism (PHPT), pituitary neuroendocrine tumors (PitNETs), and pancreatic neuroendocrine tumors. MEN1-associated insulinomas may present with multifocal disease, complicating management, while Cushing's disease is uncommon, and the coexistence of multiple functioning tumors complicates management. CASE PRESENTATION: A 28-year-old man presented with adrenocorticotropic hormone-dependent hypercortisolism and progressive cushingoid features. Pituitary Magnetic Resonance Imaging revealed a microadenoma, confirmed as a PitNET on histopathology. Concurrent PHPT and genetically confirmed MEN1 (splice-site pathogenic variant c.825-1G>A) were identified. Transsphenoidal surgery failed to achieve remission, and metyrapone provided partial control. Subtotal parathyroidectomy resulted in persistent PHPT. Imaging revealed multifocal pancreatic NETs with biochemically confirmed insulinoma. Lanreotide achieved complete resolution of hypoglycemia, while 68Ga-NOTA-exendin-4 positron emission tomography/computed tomography did not identify a dominant lesion, supporting conservative management. CONCLUSION: This case highlights the complexity of MEN1 with multiple functioning tumors and the clinical impact of hormonal interactions. It underscores the importance of multidisciplinary, individualized management, particularly when tumor multifocality limits surgical options. It also emphasizes the need to recognize complex endocrine syndromes in general clinical practice.