A form of multiple endocrine neoplasia that is characterized by the combined occurrence of tumors in the parathyroid glands, the pituitary gland, and the PANCREATIC ISLETS. The resulting clinical signs include hyperparathyroidism; hypercalcemia; hyperprolactinemia; CUSHING disease; gastrinoma; and zollinger-ellison syndrome. This disease is due to loss-of-function of the MEN1 gene, a tumor suppressor gene (genes, tumor suppressor) on CHROMOSOME 11 (Locus: 11q13).