Medical Articles

Title: Gastrin
Date: 07-Oct-2012

By N. Mohanaraja   Head of Department (Biochemistry)
     Susan George   Former Head of Department (Biochemistry)

Test Overview
The gastrin test measures the level of the hormone gastrin in the blood. Gastrin is produced by special cells called G cells in the stomach lining. When food enters the stomach, G cells trigger the release of gastrin in the blood; as blood levels of gastrin rise, the stomach releases acid (gastric acid) that helps break down and digest food. When enough gastric acid has been produced by the stomach, gastrin levels in the blood drop.

Gastrin also has minor effects on the pancreas, liver, and intestines. Gastrin helps the pancreas produce enzymes for digestion and helps the liver produce bile. It also stimulates the intestines to help move food through the digestive tract.

The level of gastrin in the blood varies throughout the day, but it is usually lowest in the morning.



Sometimes a gastrin test is performed after consuming a high-protein diet or after injecting the digestive hormone secretin into a vein. This is called an intravenous secretin test.


Why It Is Done
A gastrin test may be done to:

  • Determine whether people with recurring stomach or duodenal ulcers (that are not responding to usual treatment) have Zollinger - Ellison syndrome or G-cell hyperplasia, which is an abnormal growth of G cells, which line the stomach.
  • Help diagnose pernicious anemia, although other tests are needed to confirm a diagnosis.


How To Prepare

  • Patient to fast for 12 hours prior to test.
  • No alcohol to be consumed 24 hours prior to test.
  • Water can be consumed normally up to 1 hour prior to test . Chewing gum and smoking cigarettes are not allowed for 4 hours prior to test.
  • Acid-reducing medications, such as cimetidine (Peptol), nizatidine (Axid AR), famotidine (Pepcid), or ranitidine (Zantac), or the proton pump inhibitors lansoprazole (Prevacid), omeprazole (Losec), pantoprazole (Pantoloc), esomeprazole (Nexium), rabeprazole (Pariet), may need to be temporarily stopped before this test
  • The use of medication, such as Tums or Rolaids, needs to be stopped the night before the test.
  • Patient to rest quietly for 30 minutes before the test as stress can affect gastrin levels.


Results
The gastrin test measures the level of the hormone gastrin in the blood.


Normal values
The range of normal gastrin values may vary from lab to lab. Normal values may be higher in very young children and older adults.

Gastrin ≤ 100 picograms per millilitre (pg/mL)



Greater-than-Normal Values May Mean

  • Gastrin levels can be increased in G-cell hyperplasia, peptic ulcers, hypercalcemia, hyperparathyroidism, sarcoidosis, and stomach cancer. Gastrin can also be markedly increased in pernicious anemia and conditions in which the stomach is unable to produce gastric acid, such as atrophic gastritis. If it has been determined that the stomach is producing acid, very high gastrin levels (usually above 1,000 pg/mL) indicate Zollinger-Ellison syndrome. This disease may cause gastrin levels to increase as high as 450,000 pg/mL.
  • Gastrin is normally filtered by the kidneys. Kidney failure can cause increased gastrin levels.
  • Gastrin levels may be increased in people who have undergone surgery to remove a large portion of the intestines (small bowel resection).


Lower-than-Normal Values May Mean
Abnormally low gastrin levels can indicate hypothyroidism.


What Affects the Test
Factors that can interfere with the test and the accuracy of the results include:

  • Consumption of high-protein food right before the test.
  • Consumption of caffeinated beverages or alcohol right before the test.
  • The use of medications or supplements that contain calcium because this can increase gastrin level. Medications that control stomach acid can also increase gastrin levels. Examples of acid-reducing medications include cimetidine (Peptol) and the proton pump inhibitors lansoprazole (Prevacid), omeprazole (Losec), pantoprazole (Pantoloc), esomeprazole (Nexium), rabeprazole (Pariet). Anticholinergic medications and some medications used to treat depression (tricyclic antidepressants) decrease the level of gastrin.
  • The use of medications that contain atropine (such as Lomotil).
  • Abnormally low blood sugar (hypoglycemia).
  • Surgeries such as stomach ulcer surgery or a small bowel resection.
  • Kidney failure, rheumatoid arthritis, and cirrhosis (might cause gastrin levels to increase).
  • Elastic band (tourniquet) tightened for a prolonged period during phlebotomy.


What To Think About

  • Gastrin test results are most useful when they are evaluated along with medical information gathered from other examinations or tests.
  • If the patient has normal or mildly elevated gastrin levels but continue to have problems with peptic ulcers, further blood testing may be done. An intravenous secretin test helps determine whether peptic ulcers are being caused by Zollinger-Ellison syndrome. Gastrin levels generally increase by more than 200pg/ml in Zollinger-Ellison syndrome patients, but the rise/decrease is only slight in patients who do not have the syndrome.


How is the Sample Collected for Testing?
For basal serum gastrin levels, the patient must fast for at least 12 hours. Blood sample is collected into a 10mL plain tube. Serum has to separated and frozen.

 

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