Neuroendocrine tumours

A neuroendocrine tumour (NET) is a tumour of the neuroendocrine system.

The neuroendocrine system makes chemical messengers called hormones. Hormones regulate the workings of different organs in the body. Neuroendocrine cells are spread throughout the body in organs such as the stomach, bowels and lungs.

You can read more about how glands and hormones affect the body in our endocrinology service website section.

Symptoms of neuroendocrine tumours

Symptoms will depend on where in the body the NET is. A NET in your digestive system may cause pain or discomfort in the tummy area (abdomen) that comes and goes. You may feel sick (nauseated) or be sick (vomit), or there may be a change in your bowel habits (how often you pass stools). If you have a NET in the lung, it may cause chest infections and shortness of breath, or you may have a cough or cough up blood.

NETs sometimes make too much of certain types of hormone, which cause symptoms when they are released into the blood stream. The type of hormone that's overproduced depends on the gland that's affected by the tumour.

NETs that cause symptoms of carcinoid syndrome

Some NETs (more commonly NETs of the small bowel, large bowel or appendix) may overproduce a hormone-like substance called serotonin. Serotonin causes a characteristic collection of symptoms called the carcinoid syndrome.

Symptoms may include:

  • diarrhoea
  • flushing of the skin
  • wheezing (similar to asthma)
  • loss of appetite
  • weight loss.

People with carcinoid syndrome may be advised to avoid things that may trigger flushing, such as drinking alcohol or eating spicy food. You may be able to reduce diarrhoea by making changes to your diet. A specialist dietician can advise you about this.

Other NETs that cause symptoms

There are a number of other NETs that can cause specific symptoms due to the overproduction of hormones. These include insulinomas, gastrinomas, glucagonomas, VIPomas and somatostatinomoas.


These can occur in any part of the pancreas. The pancreas produces insulin, which controls the level of sugar in the blood. In people with an insulinoma, the tumour produces an abnormally high level of insulin, which causes low blood-sugar levels (hypoglycaemia).

A low blood-sugar level may cause symptoms such as:

  • headaches
  • confusion
  • trembling and palpitations
  • anxiety
  • eyesight changes
  • fits (seizures)
  • feeling weak.

A low blood-sugar level is most likely to occur first thing in the morning, when exercising or after missing a meal. You can often raise your blood-sugar level again by eating or by having a sugary drink.


Gastrinomas usually start in the pancreas or the upper part of the small bowel (duodenum). They may produce too much gastrin. Gastrin is a hormone that causes gastric acid to be made. High levels of gastric acid can lead to ulcers in the stomach, the gullet (oesophagus) and the small bowel. There may be several ulcers, which often don't respond well to the usual ulcer medicines. This is often called Zollinger-Ellison syndrome.

Common symptoms include:

  • bleeding into the stomach
  • a hole (perforation) in the wall of the stomach or small bowel
  • tummy cramps or feeling bloated (due to narrowing of part of the bowel)
  • diarrhoea
  • pale, greasy and offensive-smelling stools (steatorrhoea)
  • soreness and tightness in the gullet (oesophagitis).


These tumours occur most often in the pancreas. They usually produce too much glucagon, which is a hormone that helps control blood-sugar levels.

Common symptoms of a glucagonoma include:

  • anaemia (a low level of red blood cells)
  • weight loss
  • high blood-sugar (diabetes)
  • a skin rash
  • blood clots.


These usually occur in the pancreas. They may produce too much of a substance called vasoactive intestinal peptide.

Common symptoms include:

  • watery diarrhoea
  • low levels of potassium as a result of the diarrhoea
  • feeling weak and tired
  • feeling sick (nauseated) and being sick (vomiting).


Somatostatinomas are extremely rare tumours that usually occur in the pancreas or parts of the small bowel (the duodenum or jejunum). They produce extra somatostatin.

Common symptoms of a somatostatinoma include:

  • pale, greasy and offensive-smelling stools (steatorrhoea)
  • weight loss
  • anaemia (a low level of red blood cells)
  • pain in the affected area
  • diarrhoea
  • high blood-sugar (diabetes).

NETs that don't cause symptoms

Some tumours don't overproduce hormones and may not cause symptoms. These are known as non-functioning NETs. They may be discovered by chance during an operation or a test being carried out for other reasons.

*Information provided by Macmillan cancer support

At The Christie, medical oncology lead the neuroendocrine tumour service. They also have the input of many specialists alongside oncology and endocrinology including surgeons, radiologists and pathologists.

Last updated: March 2023