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Introduction ⬇

Gastrin, a hormone secreted by the antral G cells in stomach mucosa, stimulates gastric acid production and affects antral motility and secretion of pepsin and intrinsic factor. Gastrin values follow a circadian rhythm and fluctuate physiologically in relation to meals. The lowest values are between 3:00 a.m. (0300 hours) and 7:00 a.m. (0700 hours).

Measurement of serum gastrin is generally used to diagnose stomach disorders such as gastrinoma and Zollinger-Ellison syndrome (increased production of gastrin as a result of a tumor in the pancreas) in the presence of hyperacidity. (Gastric hyperacidity must be documented.)

Normal Findings ⬆ ⬇

<180 pg/mL or <86 pmol/L

Procedure ⬆ ⬇

  1. Obtain a 5-mL venous blood sample (red-topped tube) from a fasting patient. Serum is required.

  2. Freeze if not tested immediately. If the patient has not been fasting, this must be noted because values are different. Label the specimen with the patient’s name, date and time of collection, and test(s) ordered. Place the specimen in a biohazard bag.

  3. Observe standard precautions.

Clinical Implications ⬆ ⬇

  1. Increased gastrin levels are found in the following conditions:

    1. Stomach carcinoma (reduction of gastric acid secretion)

    2. Gastric and duodenal ulcers

    3. Zollinger-Ellison syndrome (>500 pg/mL or >240 pmol/L)

    4. Pernicious anemia

    5. Gastric carcinoma

    6. End-stage kidney disease (gastrin metabolized by the kidneys)

    7. Antral G-cell hyperplasia

    8. Vagotomy without gastric resection

    9. Hyperparathyroidism

    10. Pyloric obstruction

  2. Decreased gastrin levels occur in the following conditions:

    1. Antrectomy with vagotomy

    2. Hypothyroidism

Interventions ⬆ ⬇

Pretest Patient Care

  1. Explain test purpose and procedure.

  2. Remind the patient that fasting from food and all beverages except water is required for 12 hours preceding the test. Alcohol should be avoided for 24 hours. No radioisotopes for 1 week prior to testing.

  3. Note if specimen is postprandial. (If after eating, note what was eaten.)

  4. Follow guidelines in Chapter 1 for safe, effective, informed pretest care.

Posttest Patient Care

  1. Have patient resume normal activities.

  2. Review test results; report and record findings. Modify the nursing care plan as needed. Follow-up testing using gastric stimulation or gastrin suppression may be indicated.

  3. Follow guidelines in Chapter 1 for safe, effective, informed posttest care.

Interfering Factors ⬆

Values will be falsely increased in nonfasting patients, older adults, and patients with diabetes taking insulin as well as in patients after they have undergone gastroscopy and those taking H2 secretion blockers (cimetidine), steroids, and calcium. A protein meal can elevate gastrin markedly.