Gastrin Level, Zollinger-Ellison Syndrome

Sample

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

Purpose of the test (Indications)

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

Precautions

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

Pathophysiology

1. Gastrin is a hormone produced by the antral cells (G- cells) in the stomach mucosa.
   1. Other sources of production are G cell of the duodenum and delta cells of the pancreas.

2. Gastrin exists in different forms like:
   1. Small gastrin has 17 amino acids polypeptide.
   2. large gastrin has 34 amino acid polypeptides.
   3. Mini gastrin has 14 amino acids.
3. Gastrin is produced from the pregastrin which has 101 amino acids and it cleaves into gastrin.
4. Gastrin from the three sources goes into circulation and then to the liver.
   1. From liver stimulates parietal cells to produce hydrochloric acid (HCl).

5. Gastrin functions are:
   1. Stimulates gastric acid production (potent stimulator).
   2. Regulate antral motility.
   3. Control secretion of pepsin.
   4. control secretion of intrinsic factor.
   5. Secretion from the intestinal mucosa.
   6. Stimulate hepatic bile secretion.
   7. Secretion of pancreatic HCO3- and enzymes.
   8. Gastrin increases:
      1. Gastric Motility.
      2. Intestinal motility.
      3. Mucosa growth.
      4. Blood flow to the stomach.
6. Gastrin secretion has diurnal variation.
   1. It’s the lowest value is 3 a.m to 7 a.m.
7. Normal gastric physiology:
   1.  when food enters the stomach it changes pH to alkaline.
   2. This alkaline pH stimulates gastrin secretion to produce acid from parietal cells.
   3. Now low pH stops further production of Gastrin.
      1. Secretion of gastrin:
         1. Maximal at Antral pH of 5 to 7.
         2. Reduced 80% at a pH of 2 to 5.
         3. Inhibited at pH of 1.

8. Zollinger Ellison syndrome is a gastrin-producing tumor of pancreatic origin with a high serum level of gastrin.
   1. Zollinger-Elison syndrome is due to non-beta cell tumors of the pancreas which will produce a large amount of gastrin.
9. G-cell hyperplasia leads to high serum gastrin levels.
   1. Above both condition(No 8 and 9) leads to an aggressive peptic ulcer.
10. Gastrin level will be normal in the routine peptic ulcer.
11. The Patient with antacid therapy or atrophic gastritis has a high level of gastrin.
12. Gastrin stimulation test is done by giving calcium or secretin.
13. Gastrin secretion stimuli are:
    1. Partially digested food.
    2. Alcohol, and caffeine.
    3. Insulin-induced hypoglycemia.
    4. The smell of food, swallowing, and chewing.
    5. Calcium.
    6. Amino acids like glycine, tryptophan, and phenylalanine.
    7. Pancreatic islet tumors (non-β cells) produce large amounts of gastrin.
       1. Gastrin values follow a circadian rhythm and fluctuate physiologically in relation to meals.

Normal

Source 1

Age	pg/mL
Cord blood	20 to 290
0 to 4 days	120 to 183
Child	<10 to 125
!6 to 60 years	25 to 90
>90 years	<100

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 yreas = 25 to 90 pg/mL.
• Over 60 years = <100 pg/mL.

Gastrin Level and its relation to diseases:

Gastrin level	Causes (Interpretations)
>100 to <500 pg/mL	Pheochromocytoma
	Malignant carcinoma of the stomach
	Peptic ulcer
	Cirrhosis of the liver
	Hyperthyroidism
	Hyperparathyroidism
	Renal failure
	Rheumatoid arthritis
>500 to <1000 pg/mL	Pheochromocytoma
	Renal failure
	Hyperparathyroidism
	Zollinger Ellison syndrome
	Pernicious anemia
>1000 pg/mL	Zollinger Ellison syndrome
	Pernicious anemia

Increased gastrin level is seen in:

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.

Decreased Gastrin level is seen in:

1. Hypothyroidism.
2. Antrectomy with a vagotomy.

Zollinger-Ellison syndrome

1. Pathophysiology:
   1. This is a gastrin-producing pancreatic tumor.
   2. Non-beta cell tumors of the pancreas produce excessive gastrin.
   3. The G cells hyperplasia of the stomach can also give the picture of Zollinger Ellison syndrome.
   4. The patient has aggressive peptic ulcer disease.
   5. These patients have recurrence and complications.
2. Signs and symptoms:
   1. These patients have multiple ulcers in the antrum,  the duodenum, and even the jejunum.
   2. The ulcers are multiple.
      1.  There is abdominal pain.
      2. There are burning and discomforts 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 weight loss and decreased appetite.
   3. The gastrin level is normal in the routine peptic ulcers.
   4. The gastrin level is normal in the routine peptic ulcer disease while it is high in Zollinger Ellison syndrome and the 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.
3. Diagnosis:
   1. Advise Gastrin stimulation test using calcium or secretin.
   2. The patients mostly have fasting gastrin levels>500 pg/mL or >500 ng/L.
   3. The gastrin level may reach 400,000 pg/mL.
   4. 90% of the Zollinger-Ellison syndrome patients have borderline gastrin fasting levels 100 to 500 pg/mL.
   5. and these patients will show an increase of 100 pg/mL above the baseline in response to secretin stimulation. 
   6. Similar results are seen in patients with gastrinomas when calcium infusion test is given.

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