Gastrin

What is gastrin?

Gastrin is a hormone that coordinates certain functions within your digestive system. Hormones are chemicals in your bloodstream that tell different parts of your body what to do and when to do it.

What does gastrin do?

Gastrin has several important functions, such as:

• Stimulates your stomach to release gastric acid (hydrochloric acid).
• Stimulates muscle contractions in your stomach (your gastric motility).
• Stimulates your stomach lining (mucosa) to constantly replenish itself.
• Together with cholecystokinin, triggers your gallbladder and pancreas to contract.

What’s the difference between gastrin and gastric acid?

Gastrin, the hormone, is the chemical signal that triggers gastric acid to release into your stomach. Gastric acid activates the digestive enzyme, pepsin. These are the main ingredients in your gastric juices.

Where is gastrin produced?

Organs in your digestive system produce and release gastrin in coordination with digestive processes. The hormone comes from cells in the lining of your organs, called G-cells (which stands for gastrin cells).

Most gastrin comes from your stomach, specifically the bottom part (the antrum). The gastric glands within your stomach lining contain G-cells. Your duodenum and pancreas also make some gastrin.

What stimulates gastrin release?

Your brain and digestive system are in constant communication through your vagal nerves, which pass information back and forth. So, just the anticipation of eating is enough to get the process started.

Vagal nerve fibers in your brain signal to those in your stomach, telling them to get ready for digestion by releasing gastrin. Once you start eating, nerves in your stomach detect food inside and release more.

Some of the signals that stimulate gastrin to release include:

• Rising pH levels in your stomach (when there’s less acid).
• Stretching of your stomach walls to accommodate food.
• The presence of particular foods, especially proteins.

Gastrin stimulates the release of gastric acid, which, in turn, activates pepsin. These substances help break down proteins in your stomach. Gastrin also activates your stomach muscle movements.

What stops the release of gastrin?

Gastrin stops releasing when your food empties from your stomach into your duodenum, triggering the next phase of digestion. As food leaves and acid levels in your stomach rise, gastrin starts to reduce.

Food entering your duodenum triggers your gallbladder and pancreas to release their digestive juices. Then, your digestive system releases the hormone somatostatin, which turns the other hormones off.

What medical test checks gastrin levels?

A gastrin test is a type of blood test that checks the levels of gastrin circulating in your blood. A healthcare provider draws a small sample of your blood through a needle and sends it to a lab.

Why do my gastrin levels matter?

Healthcare providers may check your gastrin levels to make sure they aren’t too high. While low gastrin levels rarely occur, high gastrin levels can indicate certain gastrointestinal diseases and conditions.

What do elevated gastrin levels mean?

Elevated gastrin levels are known as hypergastrinemia. Sometimes, hypergastrinemia means you have gastrin-secreting tumors (gastrinomas). These can occur in your pancreas or duodenum.

Other times, hypergastrinemia can be a sign that something is inhibiting gastric acid in your stomach. Low gastric acid triggers more gastrin to release and inhibits the signals that normally turn gastrin off.

What do high gastrin levels do?

Higher gastrin levels can cause higher levels of gastric acid in your stomach and duodenum. Too much acid can erode the mucous lining in your stomach and duodenum, causing ulcers (peptic ulcer disease).

Too much stomach acid can also contribute to chronic acid reflux (GERD). Your provider might want to check your gastrin levels if you have peptic ulcer disease or GERD that hasn’t improved with medication.

What conditions and disorders could involve high gastrin levels?

You might have high gastrin and high gastric acid levels if you have gastrinomas. These are a type of pancreatic neuroendocrine tumor (PET) that secretes gastrin. They can be cancerous or noncancerous.

Conditions that cause gastrinomas include:

• Zollinger-Ellison syndrome.
• Multiple endocrine neoplasia type 1 (MEN1).

Conditions that cause high gastrin and high gastric acid without gastrinomas include:

• Chronic kidney failure.
• Gastric outlet obstruction (GOO).

You might have high gastrin with low gastric acid if you have reduced gastric acid production. This could be due to atrophic gastritis, when the acid-producing cells in your stomach lining waste away (atrophy).

Major causes of atrophic gastritis include:

• H. pylori infection.
• Autoimmune disease (autoimmune atrophic gastritis).

Other causes of reduced gastric acid production include:

• Acid-blocking medications, like H2 blockers or proton pump inhibitors.
• Vagotomy.

What should I do if I have symptoms of high gastrin levels?

Always see a healthcare provider about your gastrointestinal symptoms, especially if you have them often or you’ve had them for a long time. Symptoms related to increased gastrin might include:

• Burning or gnawing stomach pain.
• Chronic heartburn and indigestion.
• Acid backwash or regurgitation.
• Chronic sore throat and hoarseness.
• Chronic diarrhea.
• Digestive difficulties.

These symptoms could suggest high gastric acid levels, atrophic gastritis, peptic ulcer disease or GERD. While gastrin may or may not be involved, it’s important to diagnose and treat these conditions.