What causes carcinoid tumors

Carcinoid tumors are thought to develop from a type of cell called an enterochromaffin cell. These cells are found in the lining of the gastrointestinal tract and lungs, and they release hormones and other substances that can cause various symptoms. Researchers don’t know what triggers the cell growth that causes carcinoid tumors. They have, however, linked them to inherited syndromes, including:

  • Multiple endocrine neoplasia type 1 (MEN1), which causes your thyroid, parathyroid or adrenal glands to be overactive or form tumors.
  • Multiple endocrine neoplasia type 2 (MEN2), which causes your pancreas, pituitary or parathyroid to be overactive or form tumors.
  • Von Hippel-Lindau syndrome, a rare condition where benign tumors grow in various parts of your body.
  • Neurofibromatosis type 1, a rare condition where tumors grow on your skin and nerves, affecting your eyes and other parts of your body.

Additionally, certain environmental factors, such as exposure to certain chemicals, may also increase the risk of carcinoid tumors.

Risk factors

Factors that increase the risk of carcinoid tumors include:

  • Older age. Older adults are more likely to be diagnosed with a carcinoid tumor than are younger people or children.
  • Sex. Women are more likely than men to develop carcinoid tumors.
  • Family history. A family history of multiple endocrine neoplasia, type 1 (MEN 1), increases the risk of carcinoid tumors. In people with MEN 1 multiple tumors occur in glands of the endocrine system.


The cells of carcinoid tumors can secrete hormones and other chemicals, causing a range of complications including:

  • Carcinoid syndrome. Carcinoid syndrome causes redness or a feeling of warmth in your face and neck (skin flushing), chronic diarrhea, and difficulty breathing, among other signs and symptoms.
  • Carcinoid heart disease. Carcinoid tumors may secrete hormones that can cause thickening of the lining of heart chambers, valves and blood vessels. This can lead to leaky heart valves and heart failure that may require valve-replacement surgery. Carcinoid heart disease can usually be controlled with medications.
  • Cushing syndrome. A lung carcinoid tumor can produce an excess of a hormone that can cause your body to produce too much of the hormone cortisol.