Gastrin Level

What sample is needed for Gastrin Level?

1. Collect the venous blood to prepare the serum.
2. A fasting sample is taken (at least for 12 hours of fasting).
3. If the patient is not fasting, then the values will be different.
   1. The lowest values are between 3.00 a.m. and 7.00 a.m.
4. Freeze the sample if the test is not done immediately.

What are the Indications for Gastrin Level?

1. Gastrin level done in hyperacidity conditions.
2. It is done to diagnose Zollinger-Ellison syndrome.
3. This test also diagnoses G-cell hyperplasia.
4. It is done to diagnose gastrinoma.

What precautions are needed for Gastrin Level?

1. A high protein diet can increase gastrin levels 2 to 5 times the normal level.
2. Diabetic patients on insulin may give a false raised level of gastrin.
3. Patients with stomach surgery will have alkaline pH, a strong stimulant to gastrin.
4. Drugs like antacids, H2-blockers (cimetidine, ranitidine), and hydrogen pump inhibitors (Omeprazole) will increase the gastrin level.
5. Anticholinergic and tricyclic antidepressant drugs decrease the gastrin level.
6. Avoid alcohol for at least 24 hours.

How will you define Gastrin?

1. Gastrins are a group of peptide hormones secreted by the antrum of the stomach, and these are powerful inducers of the gastric secretion of HCL.
2. Food in the stomach produces Gastrin secretion in response to mechanical stress or high pH.
3. Gastrin stimulates parietal cells to produce HCL.

How will you discuss the pathophysiology of Gastrin?

1. Gastrin is a hormone produced by:
   1. Pancreatic delta cells.
   2. Duodenal G-cells.
   3. Stomach mucosa’s antral cells (G-cells).

2. There are different forms of gastrin as biologically active forms that differ only in the length of the chain of the N-terminal end  like:
   1. Small gastrin has 17 amino acids polypeptide (little gastrin G17).
   2. Big gastrin comprises 34 amino acid polypeptides (Big gastrin G34).
   3. Mini gastrin has 14 amino acids (G14).
3. Little and big gastrin are found in the gastric antrum and duodenum.
4. Gastrin stimulates gastric acid secretion, pepsinogen, intrinsic factor, and secretin, stimulates intestinal mucosal growth,  and increases gastric and intestinal motility.
5. Gastrin is produced from pregastrin, which has 101 amino acids and cleaves into gastrin.
6. Gastrin from the three sources goes into circulation and then to the liver.
   1. The liver stimulates parietal cells to produce hydrochloric acid (HCl).

How will you interpret gastrin action?

• Gastrin is in the normal range for peptic ulcers without Zollinger-Ellison syndrome.

How will you describe the Gastrin functions:

1. Stimulates gastric acid production (potent stimulator).
2. Gastrin overproduction causes ulcers in the upper gastrointestinal tract.
3. Regulate antral motility.
4. Control secretion of pepsin.
5. Control secretion of intrinsic factors.
6. Secretion from the intestinal mucosa.
7. Stimulate hepatic bile secretion.
8. Secretion of pancreatic HCO3- and enzymes.
9. Gastrin increases:
   1. Gastric Motility.
   2. Intestinal motility.
   3. Mucosa growth.
   4. Blood flow to the stomach.
10. Gastrin secretion has diurnal variation.
    1. Its lowest value is 3 a.m. to 7 a.m.

What is the normal Gastrin Level?

Source 1

Source 2

• Adult = 0 to 180 pg/mL or 0 to 180 ng/L.

Source 6

• Adult = 0 to 180 pg/mL  (0 to 180 ng/L).
• Child = 0 to 125 pg/mL.
• Levels are higher in elderly patients.

Source 4

• Adult = <25 to 100 pg/mL  (<12 to 48 pmol/L)
• Children = 10 to 125 pg/mL  (5 to 60 pmol/L)
• Postprandial = 95 to 140 pg/mL  (46 to 67 pmol/L)

Another source

• Children = 10 to 125 pg/mL.
• Postprandial = 95 to 140 pg/mL.
• Levels are higher in elderly patients.

Another source

• Child = <10 to 125 pg/mL
• Adult 16 to 60 years = 25 to 90 pg/mL.
• Over 60 years = <100 pg/mL.

Gastrin Level and its relation to diseases:

What are the conditions where gastrin level is Increased?

1. Zollinger-Ellison syndrome.
2. G-cell hyperplasia.
3. Atrophic gastritis.
4. The retained antral portion after gastric surgery.
5. Gastric carcinoma.
6. Pyloric obstruction (gastric outlet obstruction)
7. Gastric and duodenal ulcer.
8. Chronic renal failure.
9. Pernicious anemia.
10. Vagotomy without gastric resection.
11. Hyperparathyroidism.

What are the conditions where gastrin level is decreased?

1. Hypothyroidism.
2. Anterectomy with a vagotomy.

Zollinger-Ellison syndrome

How will you define Zollinger-Ellison syndrome?

1. This is a disorder of autonomous gastric acid hypersecretion caused by the gastrin-secreting tumor.
2. This gastrin production may be from non-β-cells tumors often present in the pancreas.
3. Tumors are malignant in 50% of the cases, and 34% have metastatic disease.
4. Hyperplasia only occurs in 10% of the cases.

How will you discuss the pathophysiology of Zollinger-Ellison syndrome?

1. This is a gastrin-producing pancreatic tumor.
2. Non-beta cell tumors of the pancreas produce excessive gastrin.
3. The G cell’s hyperplasia of the stomach can also give a picture of Zollinger-Ellison syndrome.
4. The patient has aggressive peptic ulcer disease.
5. These patients have recurrence and complications.

How will you describe the signs and symptoms of Zollinger-Ellison syndrome?

1. These patients have multiple ulcers in the antrum,  the duodenum, and the jejunum.
2. The ulcers are multiple.
   1.  There is abdominal pain.
   2. There is burning and discomfort in the upper abdomen.
   3. There are acid reflux and heartburn.
   4. The patient may have diarrhea.
   5. The patient may have nausea and vomiting.
   6. The patient may have bleeding in the GI tract.
   7. The patient may have weight loss and decreased appetite.
3. The gastrin level is normal in routine peptic ulcers.
4. The gastrin level is normal in routine peptic ulcer disease, while it is high in Zollinger Ellison syndrome and G-cell hyperplasia.
5. The patients on antacid or peptic ulcer disease medicines, atrophic gastritis, and patients with peptic ulcer surgery have slightly raised gastrin levels.

How will you diagnose Zollinger-Ellison syndrome?

1. Gastrin assay is the method of choice.
   1. Most patients have fasting gastrin levels>500 pg/mL or >500 ng/L (fasting level is elevated in more than 95% of the cases).
   2. The gastrin level may reach 400,000 pg/mL.
   3. Gastrin level may be >5 times the normal value (1,000 pg/mL or 1,000 ng/L). This value is diagnostic.
2. Advise Gastrin stimulation test using calcium or secretin.
   1. It is advised when the fasting level is <1,000pg/mL (1,000 ng/L) to assist the differentiation from other conditions.
3. 90% of the Zollinger-Ellison syndrome patients have borderline gastrin fasting levels of 100 to 500 pg/mL.
4. In response to the secretin stimulation test, these patients will increase 100 pg/mL above the baseline. 
5. When a calcium infusion test is given, gastrinoma patients have similar results.

Gastrin level in gastrinoma

Questions and answers: