MULTIPLE ENDOCRINE NEOPLASIA

Genetic tumor conditions

Multiple Endocrine Neoplasia (MEN) Syndromes are a collection of rare AD genetic disorders. Depending on the type of MEN you get, you’ll end up with a slew of tumors in different endocrine organs. Unfortunately these are high yield, and you must memorize them. A common test question is to provide you with one or two of the tumors, then ask you which test to order next. For example, they might say a tall thin man has mucosal tumors in his mouth, and the next test would be thyroid imaging / biopsy to rule out medullary thyroid cancer.

CARCINOID TUMORS

Serotonin belly cancer

Carcinoid tumors are slow-growing neoplasms of neuroendocrine cells, predominantly within the small intestine and GI tract. This is one of the very few tumors involving the small intestines. Carcinoid tumors produce serotonin and secrete it into the portal circulation. When that blood flow reaches the liver, the serotonin will be degraded by hepatocytes into inactive precursors like 5-HIAA (which can be tested for in urine). Neuroendocrine tumors like this stain (+) for Chromogranin A and Synaptophysin. There are no symptoms yet. 

But if the tumor metastasizes to the liver or beyond, serotonin will be able to bypass degradation and enter the general circulation. Serotonin causes symptoms like diarrhea, flushing and bronchospasms (wheezing). At this point, the disease is called Carcinoid Syndrome. When serotonin reaches the right side of the heart, it tends to cause valvular diseases (stenosis or regurgitation). Serotonin is then broken down by the lungs, sparing the left side of the heart from valvular damage. 

Serotonin is made using B3 (Niacin), so a B3 deficiency is possible, aka pellagra (diarrhea, dermatitis, dementia).