II. Physiology

  1. Polypeptide secreted by the gastric mucosa
  2. Increases secretion of Stomach digestive substances
    1. Gastric acid
    2. Pepsin
    3. Intrinsic Factor
  3. Factors that increase Gastrin
    1. Vagus Nerve Stimulation
    2. Duodenal Distention
    3. Peptides within Stomach
  4. Factor that decrease Gastrin
    1. Secretin
    2. Gastric inhibitory peptide
    3. Increased Stomach acidity (low pH)

III. Labs

  1. Normal Serum Gastrin: <180 pg/ml

IV. Causes: Increased - Most important causes

  1. Medications (most common cause)
    1. Proton Pump Inhibitors (e.g. Omeprazole)
      1. Associated with 2-5 fold increase in Gastrin level
    2. H2 Blockers
  2. Pernicious Anemia
    1. Very low Stomach acid level (contrast with Zollinger-Ellison)
  3. Zollinger-Ellison Syndrome or Gastrinoma (rare)
    1. Very high Gastrin level
    2. Gastrin Level remains increased despite withdrawal of Proton Pump Inhibitors and other possible causes
    3. High Stomach acid level
      1. Measured with nasogastric suction over one hour
      2. Contrast with very low Stomach acid level in Pernicious Anemia

V. Causes: Increased - Other Causes

  1. Hyperparathyroidism
  2. Retained gastric antrum
  3. Chronic atrophic Gastritis
  4. Pyloric obstruction
  5. Gastric neoplasm
  6. Chronic Renal Failure

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