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Gastrin

SI UNITS (recommended)

CONVENTIONAL UNITS

(Gastrointestinal Hormone – Marker for Gastric Acid Regulation, Zollinger–Ellison Syndrome & G-cell Function)

Synonyms

  • Gastrin
  • Serum gastrin
  • G-17 / G-34 (gastrin isoforms)
  • G-cell hormone
  • Hypergastrinemia marker

Units of Measurement

  • pmol/L
  • ng/L
  • ng/dL
  • ng/100 mL
  • ng%
  • pg/mL
  • mU/L

Key Conversions

(Using MW ≈ 2,100 Da for gastrin-17 – assay dependent)

1 pg/mL ≈ 0.48 pmol/L
 1 pmol/L ≈ 2.1 pg/mL
 1 pg/mL = 1 ng/L
 1 ng/dL = 0.01 ng/mL = 10 pg/mL
 ng/100 mL = ng% = ng/dL
 mU/L: activity-based unit (not convertible to mass)

(Mass-based ↔ activity-based units cannot be interconverted.)

Description

Gastrin is a peptide hormone secreted by G-cells in the gastric antrum, duodenum, and pancreas.

Primary functions:

  • Stimulates gastric acid secretion (H⁺)
  • Increases gastric motility
  • Enhances growth of gastric mucosa
  • Regulates meal-stimulated digestion

Serum gastrin is a critical biomarker for:

  • Zollinger–Ellison syndrome (ZES)
  • Gastrinoma
  • Chronic PPI therapy effects
  • Atrophic gastritis / pernicious anemia
  • Helicobacter pylori–related disorders

Physiological Role

  • Gastrin release stimulated by:
    • Peptides & amino acids
    • Gastric distension
    • Vagal (acetylcholine) stimulation
  • Inhibited by:
    • Low gastric pH (<3.0)
    • Somatostatin

Gastrin promotes:

  • Parietal cell HCl secretion
  • ECL cell histamine release
  • Mucosal proliferation

Clinical Significance

High Gastrin (Hypergastrinemia)

Very important clinically.

1. Zollinger–Ellison Syndrome (ZES)

Gastrinoma → massive hypergastrinemia

  • Gastrin >1000 pg/mL (>480 pmol/L) strongly suggests ZES
  • Fasting gastric pH <2 confirms hypersecretion

2. Chronic PPI Therapy

Prolonged PPI use → compensatory ↑ gastrin due to acid suppression
Levels usually 200–500 pg/mL

3. Atrophic Gastritis / Pernicious Anemia

Low acid → G-cell hyperplasia → very high gastrin

4. H. pylori Infection

Mild–moderate gastrin elevation

5. Renal Failure

Reduced gastrin clearance → ↑ serum level

6. Gastric Outlet Obstruction / Retained Antrum Syndrome

7. G-cell Hyperplasia

Non-neoplastic cause of high gastrin

Low Gastrin

Seen in:

  • High gastric acid output
  • Stress disorders
  • Vagotomy
  • Hyperthyroidism (rare)
    Clinically less important.

Reference Intervals

(Tietz 8E + Mayo + ARUP + AGA)

Fasting Gastrin Levels

  • 13 – 115 pg/mL
     (≈ 6 – 55 pmol/L)

Interpretation

Gastrin LevelInterpretation
<115 pg/mLNormal
115–300 pg/mLMild elevation (PPI use, H. pylori)
300–1000 pg/mLModerate elevation (need gastric pH testing)
>1000 pg/mLStrongly suggests ZES/gastrinoma if gastric pH < 2

Diagnostic Uses

1. Zollinger–Ellison Syndrome Diagnosis

Key markers:

  • Fasting gastrin >1000 pg/mL
  • Gastric pH <2
  • Secretin stimulation test (paradoxical ↑ gastrin)
  • Imaging for gastrinoma

2. Gastric Acid Disorders

  • Hyperchlorhydria
  • Atrophic gastritis
  • Pernicious anemia

3. Monitoring PPI Therapy Effects

Long-term therapy increases gastrin; useful for:

  • Identifying need to reevaluate high-dose PPI therapy
  • Risk monitoring (rare ECL cell hyperplasia)

4. H. pylori Gastritis

Mild elevation due to inflammation-induced antral G-cell hyperactivity.

5. Evaluation of Refractory Ulcers

  1. Gastrinoma workup
  2. Hypersecretory states

Analytical Notes

  • Fasting sample required (8–10 hours)
  • PPIs must be stopped for 7 days if clinically safe
  • H2 blockers should be held for 48 hours
  • Hemolysis does not significantly affect results
  • Use same assay for serial monitoring

Clinical Pearls

  • Very high gastrin (>1000 pg/mL) is nearly diagnostic of ZES, but only if gastric pH < 2.
  • PPIs can mimic gastrinoma by driving gastrin above 500 pg/mL.
  • Atrophic gastritis causes high gastrin with high gastric pH (>4).
  • Secretin stimulation test: gastrin rises in ZES but suppresses in normal subjects.
  • Gastrin has a short half-life (~7 minutes); prompt sample handling matters.

Interesting Fact

Gastrin was first discovered in 1905, but its structure was solved only in 1964 - marking the beginning of modern gastroendocrinology.

References

  1. Tietz Clinical Chemistry & Molecular Diagnostics, 8th Edition - GI Hormones.
  2. ACG/AGA Guidelines - Gastric Acid Disorders.
  3. NCCN - Neuroendocrine Tumor Evaluation.
  4. Mayo Clinic Laboratories - Gastrin.
  5. ARUP Consult - Gastrinoma & Hypergastrinemia.
  6. MedlinePlus / NIH - Gastrin Test.

Last updated: January 26, 2026

Reviewed by : Medical Review Board

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