To detect an overproduction of gastrin, to help diagnose Zollinger-Ellison syndrome (ZE syndrome), to help diagnose multiple endocrine neoplasia type 1 (MEN-1) and to monitor for recurrence of a gastrin-producing tumour (gastrinoma)
A blood sample taken from a vein in your arm.
You should fast for 12 hours and avoid alcohol for 24 hours before the test. Your doctor may also ask you to stop taking certain stomach medications before the test. Gastrin can increase with medications such as proton pump inhibitors (PPI) which block acid production in the stomach and H2 blockers which reduce the amount of acid produced by the gastric parietal cells. Before a blood sample is taken for a baseline gastrin level H2 blockers including ranitidine, cimetidine, famotidine or nizatidine should be stopped for 72 hours and PPIs including omeprazole, lansoprazole or pantoprazole should be stopped for 2 weeks prior to testing.
This test measures the amount of gastrin in the blood. Gastrin is a hormone that regulates the production of acid in the stomach. It is produced by special cells called G-cells in the stomach during the digestive process. When food is eaten, the stomach becomes less acidic, promoting gastrin production. Gastrin in turn stimulates parietal cells to produce stomach acid. As acidity increases in the stomach, food is broken down and gastrin production falls. This feedback system normally results in low to moderate levels of gastrin in the blood. Rare conditions such as G-cell hyperplasia and Zollinger-Ellison (ZE) syndrome can cause an overproduction of gastrin and stomach acid. These conditions can lead to peptic ulcers that can be difficult to treat.
ZE syndrome is characterised by high gastrin levels, greatly increased stomach acid production, and by peptic ulcers due to gastrin-producing tumours called gastrinomas. Gastrinomas can form in the pancreas, the duodenum and rarely in other parts of the body. More than half of these tumours are malignant and can spread to other parts of the body, such as the liver. Even tiny tumours can produce large quantities of gastrin.
How is the sample collected for testing?
A blood sample is taken by inserting a needle into a vein in the arm.
Is any test preparation needed to ensure the quality of the sample?
You should fast for 12 hours and avoid alcohol for 24 hours prior to the test. Your doctor may also ask you to stop taking certain stomach medicines for several days before the test.
How is it used?
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.
When is it requested?
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.
What does the test result mean?
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.
Is there anything else I should know?
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.
What is Zollinger-Ellison syndrome?
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.
How long will it take to get the results of my gastrin test?
Gastrin testing is performed using specialised methods in a laboratory and not every laboratory will offer gastrin testing. In some cases, your sample may need to be sent to a reference laboratory and results may take a few weeks before they are reported.
Can’t I just take stomach medicines to treat my excess gastrin and stomach acid?