Diagnosis and Management of Multiple Endocrine Neoplasia Type 1 (MEN1)

Clinical Presentation and Diagnosis

The American Gastroenterological Association recommends that all patients with gastrinoma should be evaluated for MEN1 syndrome, with mandatory measurement of fasting calcium, parathyroid hormone, and prolactin 1, 2
MEN1 patients develop multiple pancreatic neuroendocrine tumors, with gastrinomas being the most common functional tumor (54%) and insulinomas occurring in approximately 10-30% of MEN1 cases 1
The presence of hypercalcemia in a patient with gastrinoma mandates full MEN1 evaluation, as these patients require different surgical management and lifelong surveillance 1, 2

The Endocrine Society recommends measuring parathyroid hormone (PTH) to confirm primary hyperparathyroidism, which is present in >90% of MEN1 patients and is usually the first manifestation 1, 2
Measuring fasting insulin, C-peptide, and proinsulin is recommended to screen for insulinoma 1
A 48-72 hour supervised fast is considered if insulinoma is suspected based on symptoms or biochemistry, as this will trigger hypoglycemia in most cases within 24 hours 1, 3

Multiphasic CT or MRI of abdomen and pelvis is recommended to localize gastrinoma and evaluate for other pancreatic neuroendocrine tumors 2, 3

The American College of Gastroenterology advises against interpreting elevated gastrin while patient is on PPIs, as this is the most common cause of false positives and will lead to misdiagnosis 1, 2, 3
The National Comprehensive Cancer Network recommends against assuming isolated gastrinoma, as the presence of hypercalcemia mandates full MEN1 evaluation 1, 2