Gastrin - Serum

Hormone/ Element

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No Fasting Required

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Measures gastrin hormone.

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Gastrin - Serum Test Information Guide

Why is it done?
- Measures the hormone gastrin produced by G cells in the stomach and duodenum to assess gastric acid secretion and evaluate gastroenterological disorders
- Diagnostic indications: Suspected Zollinger-Ellison Syndrome (ZES), recurrent or refractory peptic ulcer disease, chronic gastroesophageal reflux disease (GERD), unexplained diarrhea, and evaluation of pernicious anemia
- Monitoring purposes: Follow-up of diagnosed gastrin-secreting tumors (gastrinomas), assessment of treatment response in ZES, and evaluation of post-surgical complications affecting gastric acid regulation
- Timing: Typically performed when patient presents with persistent gastrointestinal symptoms, after failure of standard ulcer therapy, or during evaluation of multiple endocrine neoplasia type 1 (MEN-1)
Normal Range
- Reference Range: 0-100 pg/mL (picograms per milliliter) or 0-47 pmol/L (picomoles per liter) depending on laboratory standards
- Normal Result: Serum gastrin levels within the established reference range indicate normal gastric acid regulation and normal G cell function
- Elevated Result: Levels >100 pg/mL (>47 pmol/L) are considered elevated and may indicate pathological gastrin production or gastrin-secreting tumors
- Significantly Elevated: Levels >1000 pg/mL (>473 pmol/L) are highly suggestive of Zollinger-Ellison Syndrome, particularly when accompanied by elevated gastric acid output
- Units of Measurement: pg/mL (picograms per milliliter), pmol/L (picomoles per liter), or mIU/L depending on laboratory methodology and region
Interpretation
- Low-Normal Levels (0-50 pg/mL): Typically indicates normal gastric physiology; rules out gastrin-secreting pathology; consistent with normal response to gastric acid stimulation
- Borderline Elevated (100-300 pg/mL): May be seen in achlorhydria, pernicious anemia, chronic gastritis with atrophic changes, or following gastric surgery; requires clinical correlation and confirmatory testing
- Moderately Elevated (300-1000 pg/mL): Suggestive of possible gastrinoma or ZES; warrants secretin stimulation test and gastric pH measurement to confirm diagnosis; may also indicate chronic use of proton pump inhibitors
- Markedly Elevated (>1000 pg/mL): Highly diagnostic for Zollinger-Ellison Syndrome when accompanied by low gastric pH (<2) and elevated basal acid output; strongly suggests gastrin-secreting neuroendocrine tumor
- Factors Affecting Results: Recent food intake (should be fasting), proton pump inhibitor use (increases levels), H2-receptor antagonist use, stress, renal insufficiency, liver disease, and timing relative to meals
- Clinical Significance Patterns: Combined with gastric pH: Low pH + high gastrin = ZES; High pH + high gastrin = achlorhydria; Low pH + low gastrin = normal or GERD
Associated Organs
- Primary Organs Involved: Stomach (G cells in gastric antrum and fundus), duodenum (G cells in duodenal mucosa), pancreas (if gastrinoma present), and parietal cells of gastric mucosa
- Conditions Associated with Elevated Gastrin: Zollinger-Ellison Syndrome (gastrin-secreting pancreatic or duodenal tumors), atrophic gastritis, pernicious anemia, achlorhydria, chronic renal failure, and multiple endocrine neoplasia type 1
- Conditions Associated with Suppressed Gastrin: Post-gastrectomy states (particularly antrectomy), normal gastric physiology with adequate acid secretion, and conditions affecting gastric pH homeostasis
- Diseases Diagnosed or Monitored: Gastrinomas (neuroendocrine G-cell tumors), Zollinger-Ellison Syndrome, peptic ulcer disease with gastrin hypersecretion, and multiple endocrine neoplasia type 1 (MEN-1) associated tumors
- Potential Complications from Abnormal Results: Severe peptic ulcer disease with perforation risk, severe esophagitis and Barrett's esophagus from gastrin-driven acid hypersecretion, chronic diarrhea, malnutrition, and complications from metastatic gastrinomas
Follow-up Tests
- Confirmatory Tests for Elevated Gastrin: Secretin stimulation test (gold standard for ZES diagnosis - paradoxical gastrin increase >200 pg/mL is diagnostic), gastric pH measurement (<2 indicates ZES), basal acid output (BAO) measurement
- Imaging Studies: CT or MRI of abdomen and pelvis to localize gastrinoma, endoscopic ultrasound (EUS) for small tumor detection, somatostatin receptor scintigraphy (SRS), positron emission tomography (PET) scan for metastatic disease
- Additional Diagnostic Tests: Upper endoscopy for ulcer assessment and tissue biopsy, vitamin B12 level (for pernicious anemia correlation), intrinsic factor antibodies, parietal cell antibodies, assessment for MEN-1 (prolactin, PTH, calcium)
- Monitoring Frequency for Diagnosed Conditions: ZES patients: Gastrin levels every 3-6 months initially, then annually if stable on treatment; Gastrinoma post-resection: Gastrin levels at 1 week, 1 month, then 3-6 months post-op; MEN-1 patients: Annual gastrin screening
- Related Complementary Tests: Chromogranin A (neuroendocrine marker), 24-hour urine 5-hydroxyindoleacetic acid (5-HIAA), pancreatic polypeptide levels, vasoactive intestinal peptide (VIP), substance P, and other neuroendocrine markers
Fasting Required?
- Fasting Requirement: YES - Fasting is required for accurate gastrin measurement
- Fasting Duration: Minimum 12 hours overnight fast is required; ideally drawn in the morning after overnight fast (typically 6-12 hours of nothing by mouth)
- Special Instructions: Do not eat or drink anything except water after midnight the night before; specimens must be drawn in the morning before any meal or beverage consumption
- Medications to Avoid/Discontinue: CRITICAL: Discontinue proton pump inhibitors (PPI) at least 1 week prior to testing as they elevate gastrin levels; discontinue H2-receptor antagonists 48 hours before test; hold antacids 24 hours before; do not use anticholinergic medications; hold calcium supplements which affect gastrin
- Other Patient Preparation Requirements: Patient should be rested and relaxed before blood draw as stress affects gastrin; collect blood in EDTA tube or appropriate collection tube per laboratory; keep specimen cool if delay anticipated; notify laboratory of any medications patient is unable to discontinue; document current medications on requisition

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