Gastrin

The gastrin test is usually requested to help detect high levels of gastrin which increases acid production in the stomach. It is used to help diagnose gastrin-producing tumours called gastrinomas, Zollinger-Ellison (ZE) syndrome, and hyperplasia of G-cells, specialised cells in the stomach that produce gastrin. It may be measured to screen for the presence of multiple endocrine neoplasia type I (MEN ) It may be used if a person has abdominal pain, diarrhoea and recurrent peptic ulcers.

A gastrin test may also be requested to look for recurrence of disease following surgical removal of a gastrinoma.

Sometimes a gastrin stimulation test may be used if a gastrin result is not very elevated, but the doctor still suspects that the patient's symptoms are due to a gastrinoma. This procedure involves collecting a baseline gastrin sample, giving the patient a chemical (typically the hormone secretin) to stimulate gastrin production, and then taking additional gastrin samples at timed intervals.

A measurement of gastric acid level (pH) may sometimes be used with or following a gastrin test to help diagnose ZE syndrome.

A gastrin test may be used when you have diarrhoea, stomach pain, and/or recurrent peptic ulcers that your doctor suspects are due to excess gastrin production. A gastrin stimulation test may be used when a gastrin level is moderately elevated and the doctor suspects the patient has a gastrinoma. When you have had a gastrin-producing tumour removed, a gastrin test may be used periodically as a screening test to monitor for recurrence.

Moderately increased levels of gastrin may be seen in a variety of conditions such as ZE syndrome, G-cell hyperplasia, atrophic gastritis, pernicious anaemia, a pyloric obstruction (blockage at the junction of the stomach and duodenum), Helicobacter pylori infection of the stomach and chronic kidney failure.

Gastrin levels can increase with age and with prolonged use of medicines such as antacids and proton pump inhibitors that neutralise or reduce the production of stomach acid. They may also be elevated in patients who are not fasting and for a day after drinking alcohol.

Greatly increased levels of gastrin in patients who have symptoms and levels of gastrin that increase al lot during a gastrin stimulation test both indicate that a person may have ZE syndrome and one or more gastrinomas. Imaging tests may be used to follow-up to high gastrin concentrations to help find the location of the gastrinoma(s). The quantity of gastrin produced is not related to either the tumour size or to the number of tumours. Even tiny tumours can produce large amounts of gastrin.

Gastrin levels that were initially low after the surgical removal of a gastrinoma and then increase may signal a return of the tumour. Concentrations that do not decrease after treatment may indicate that the treatment has not been fully effective.

Gastrinomas can affect anyone, but patients who have an inherited condition called MEN-1 (Multiple Endocrine Neoplasia, type 1) are at an increased risk. These people have genetic alterations that increase their lifetime risk of developing tumours in their pancreas or in another of their endocrine glands. 

It is important to note that most stomach ulcers are not due to gastrinomas. They are commonly associated with Helicobacter pylori infections and sometimes with the use of NSAIDs (nonsteroidal anti-inflammatory medicines) such as ibuprofen.

Increases in gastrin concentration with age may reflect a general decrease in the ability to produce stomach acid.

Zollinger-Ellison (ZE) syndrome is a rare disease of the gastrointestinal tract. It causes severe and repeated peptic ulcers in the stomach, duodenum and/or the upper portion of the small intestine. The ulcers are caused by a greatly increased amount of stomach acid due to high levels of gastrin, the hormone that stimulates stomach acid production. In ZE, high gastrin levels are caused by gastrin-producing tumours called gastrinomas, which usually form in the duodenum but can be found in the pancreas and rarely in other parts of the body. More than half of them are malignant and may spread to other parts of the body, such as the liver. The tumours must be removed surgically, and sometimes total removal of the stomach is necessary to control the acid production.