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Symptoms of neuroendocrine tumours (NETs)

Neuroendocrine tumours (NETs) may not cause any signs or symptoms if they grow slowly and don’t make too much of a certain hormone. Signs and symptoms may appear as the tumour grows or if hormones are released by the tumour (if it is a functional tumour). Other health conditions can cause the same symptoms as NETs.

The signs or symptoms of NETs vary depending on where the tumour develops in the body.

Symptoms of gastrointestinal neuroendocrine tumours (GI NETs)

Gastrointestinal neuroendocrine tumours (GI NETs) can develop in any part of the gastrointestinal tract, including the small or large intestine and stomach. Signs or symptoms of GI NETs may include:

  • discomfort or pain in the abdomen or rectum
  • nausea and vomiting
  • diarrhea
  • bleeding from the rectum or blood in the stool
  • anemia – may cause fatigue
  • heartburn or indigestion
  • stomach ulcers – can cause heartburn, indigestion and pain in the chest or abdomen
  • weight loss
  • blockage in the intestine (bowel obstruction) – may cause pain in the abdomen or constipation

Carcinoid syndrome is a group of symptoms caused by a NET releasing large amounts of serotonin and other chemicals into the blood. Carcinoid syndrome may happen in people with any type of NET. It most commonly occurs with NETs of the small intestine that have spread to the liver (liver metastases). The signs or symptoms of carcinoid syndrome include:

  • flushing of the skin, mainly the face and neck
  • diarrhea
  • wheezing and difficulty breathing
  • fast or irregular heartbeat
  • low blood pressure
  • heart damage (carcinoid heart disease)

Carcinoid crisis is a severe case of flushing, low blood pressure, difficulty breathing and an irregular heartbeat. It may be triggered by anesthesia, surgery or other treatments. Carcinoid crisis is a serious and possibly life-threatening problem that needs to be treated right away. A drug called octreotide (Sandostatin) can be given to treat and reduce the risk of carcinoid crisis.

Symptoms of lung neuroendocrine tumours (lung NETs)

Lung neuroendocrine tumours (lung NETs) usually develop in the airways (bronchi). Signs or symptoms of lung NETs may include:

  • a cough that doesn’t go away
  • coughing up blood
  • difficulty breathing
  • fatigue
  • pneumonia
  • carcinoid syndrome – may include flushing of the skin, diarrhea and wheezing

Cushing syndrome is a group of symptoms caused by too much cortisol in the body. Cushing syndrome may happen in people with NETs, including some lung and pancreatic NETs, when too much adrenocorticotropic hormone (ACTH) is released. This causes too much cortisol to be made by the adrenal glands. The signs or symptoms of Cushing syndrome include:

  • weight gain
  • a red, round and full face
  • muscle weakness
  • increased hair growth on the face and body
  • a buildup of fat between the shoulders or above the collar bone
  • purple lines on the skin
  • high blood pressure
  • high blood sugar (glucose) levels
  • changes in mood and behaviour

Symptoms of pancreatic neuroendocrine tumours (pNETs)

Signs or symptoms of pancreatic neuroendocrine tumours (pNETs) depend mainly on the type of hormone released by the tumour. The signs or symptoms of pNETs include:

  • low blood sugar levels (hypoglycemia) – may cause sweating, shakiness, dizziness, extreme hunger and problems concentrating
  • high blood sugar levels (hyperglycemia) – may cause extreme thirst and frequent urination, diarrhea and fatty stools
  • stomach ulcers – may cause heartburn, indigestion and pain in the chest or abdomen
  • weight loss
  • patches of red, itchy and painful skin
  • jaundice
  • blood clots
  • Cushing syndrome – may include a red, round and full face

Zollinger-Ellison syndrome is a condition caused by too much gastrin in the body. This increases the amount of stomach acid made, which can eventually lead to ulcers of the stomach or small intestine. Zollinger-Ellison syndrome may happen in people with gastrin-producing NETs of the pancreas or small intestine (gastrinoma). The signs or symptoms of Zollinger-Ellison syndrome include:

  • pain in the abdomen
  • severe diarrhea
  • heartburn
  • nausea and vomiting, sometimes vomiting blood
  • weight loss


A type of neurotransmitter (a chemical that transmits signals or impulses from one neuron, or nerve cell, to another neuron cell or other specialized cells) that causes blood vessels to narrow and regulates the movement of the intestines.

Serotonin is made by specialized cells of the neuroendocrine system that are found mainly in the digestive system. It is also found in the brain, pineal gland and platelets (blood cells that help blood to clot).


Infection of one or both lungs caused by bacteria, viruses or fungi. Signs and symptoms include fever, chills, cough with sputum (phlegm), chest pain and shortness of breath.


A hormone that helps the body use glucose (sugar), protein and fat.

Cortisol is made by the adrenal gland. It can also be produced in the lab.

Also called hydrocortisone.


A hormone that causes the stomach to release an acid that helps to digest food.

Gastrin is made by cells in the stomach.