Parathyroid tumors
Hyperparathyroidism is the most common manifestation of MEN 1.Clinical manifestations include urolithiasis, bone abnormalities, and, in severe cases, generalized weakness and mental or cognitive dysfunction.Hyperparathyroidism in MEN 1 differs from sporadic cases by earlier age at presentation, involvement of multiple glands, and high recurrence rate postoperatively (50% by 8-12 y after surgery).
Enteropancreatic tumors
Pancreatic islet cell tumors represent the second most common manifestation of MEN 1 and occur in 80% of patients.Nonfunctioning pancreatic endocrine tumors are the most common pancreatic tumors, occurring in 80-100% of cases
Gastrinomas are the most common cause of symptomatic disease and are found in approximately 60% of patients with MEN 1. Compared with the sporadic form of gastrinomas in Zollinger-Ellison syndrome (ZES), tumors in MEN 1 are more often duodenal, small, and multicentric, thus diminishing the probability of surgical cure. The features predictive of poor prognosis include pancreatic location of lesions, metastases, ectopic Cushing syndrome, and height of gastrin levels. Development of gastrinomas is preceded by multifocal hyperplasia of the gastrin-producing cells. Long-standing MEN 1/ZES may lead to development of gastric carcinoid tumors that might be aggressive.
Insulinomas account for approximately 20-35% of functional pancreatic islet cell tumors. Similar to gastrinomas, they can be multicentric (10-20%), where 25% metastasize either to regional lymph nodes or to the liver.
Glucagonomas occur in 3% of patients with MEN 1 and are silent or present with hyperglycemia. Only a few patients show the typical skin lesions known as necrolytic migratory erythema.
The occurrence of the watery diarrhea, hypokalemia, hypochlorhydria, and acidosis (WDHA) syndrome (incidence approximately 1%) may be due either to either a pancreatic islet cell or to a carcinoid tumor.
Pituitary tumors
These often-multicentric tumors occur in more than 50% of patients and are clinically apparent in up to 20% of patients. These tumors tend to be larger and more aggressive than those not associated with MEN 1.Prolactinomas are the most common pituitary tumor in patients with MEN 1.
Growth hormone–producing tumors account for 25% of these adenomas. Growth hormone levels rise due to autonomous secretion from the pituitary tumor or, less commonly, by production of growth hormone–releasing factor by a pancreatic or other endocrine tumor.
A pituitary tumor or carcinoid tumor that produces corticotropin can cause Cushing syndrome in patients with MEN 1. Ectopic production of corticotropin-releasing factor from a pancreatic islet cell tumor also has been described.
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