Multiple endocrine neoplasia

Published on 02/03/2015 by admin

Filed under Endocrinology, Diabetes and Metabolism

Last modified 02/03/2015

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Multiple endocrine neoplasia

1. What are the multiple endocrine neoplasia (MEN) syndromes?

2. Define MEN-1.

3. Define MEN-2A.

4. Define MEN-2B.

5. How can so many various endocrine organs be affected in these syndromes?

The cells that comprise many endocrine organs are able to decarboxylate various amino acids and convert the molecules to amines or peptides that act as hormones or neurotransmitters. These cells have been classified as amine precursor uptake and decarboxylation (APUD) cells and are considered to be embryologically of neuroectodermal origin. APUD cells contain markers of their common neuroendocrine origin, including neuron-specific enolase and chromogranin A. Neoplastic transformation of APUD cells long after organogenesis is complete appears to result from a germline mutation (loss of a tumor suppressor gene in MEN-1 or mutation of a protooncogene to an oncogene in MEN-2A and MEN-2B) in a gene that is expressed only in neuroectodermal cells. When neuroectodermal cells later migrate to specific developing organs, the genetic mutation similarly is distributed to those organs. This explains the common mutations manifested in this class of neuroendocrine tumors (NETs).

6. What is Wermer syndrome?

7. How common is Wermer syndrome?

8. Is hyperparathyroidism in MEN-1 similar to sporadic primary hyperparathyroidism?

9. What causes the hyperplasia of parathyroid glands affected by MEN-1?

10. Summarize the therapy for hyperplastic parathyroid glands.

Therapy of both sporadic adenomas and MEN-1–associated hyperplastic glands depends on surgical resection. In sporadic primary hyperparathyroidism, removal of the solitary adenoma is curative in 95% of cases. In MEN-1–associated hyperplasia, at least 3.5 hyperplastic glands must be resected to restore normocalcemia. Only 75% of patients are normocalcemic postoperatively; 10% to 25% of patients are rendered hypoparathyroid. Unfortunately, the parathyroid remnants in the patient with MEN-1 have a great propensity to regenerate; 50% of patients become hypercalcemic again within 10 years of surgery. This recurrence rate dictates that surgery be delayed until complications of hypercalcemia are imminent or gastrin levels are elevated, as discussed later. Recurrence may be treated surgically or with cinacalcet, which acts at the calcium-sensing receptor, to reduce parathyroid hormone (PTH) secretion.

11. How common is neoplastic transformation of pancreatic islet cells in MEN-1?

12. What types of pancreatic tumors are found in MEN-1 syndrome?

13. What is the most common type of functional pancreatic tumor in MEN-1?

14. Describe the symptoms of gastrinomas associated with MEN-1.

15. What other conditions may cause hypergastrinemia?

16. How are gastrinomas distinguished from other causes of hypergastrinemia?

17. What is the second most common type of functional pancreatic tumor in MEN-1?

18. What other pancreatic tumors may be seen in MEN-1?

19. How are the most common pancreatic tumors of MEN-1 treated?

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