Zollinger‑Ellison Syndrome (Gastric Neuroendocrine Tumor)
Overview
Zollinger‑Ellison syndrome (ZES) is a rare disorder in which one or more gastrin‑producing tumors (gastrinomas) arise in the pancreas, duodenum, or, less commonly, the stomach. The excess gastrin stimulates the stomach lining to secrete large volumes of hydrochloric acid, leading to severe, recurrent peptic ulcers and diarrhea.
Although ZES is a type of gastric neuroendocrine tumor (NET), the term “gastric NET” also includes other NET subtypes; this guide focuses on ZES‑related NETs.
- Incidence: Approximately 0.5–2 cases per million people per year.1
- Age: Most patients are diagnosed between 30 and 60 years of age, but cases in children and the elderly are reported.
- Gender: Slight male predominance (≈55% male).2
- Associated conditions: About 20–30% of cases occur as part of Multiple Endocrine Neoplasia type 1 (MEN‑1), a hereditary syndrome.
Symptoms
Symptoms arise from two main mechanisms: hyperacidic gastric secretions and the mass effect of the tumor itself.
Gastro‑intestinal symptoms
- Refractory peptic ulcers: Often multiple, located in the duodenum and sometimes the jejunum; they may not heal with standard therapy.
- Abdominal pain: Burning or gnawing pain that may improve with meals (due to ulcer healing) or worsen with food (due to increased acid).
- Chronic diarrhea: Stools are watery, sometimes greasy; caused by acid inactivation of pancreatic enzymes.
- Steatorrhea (fatty stools): Malabsorption of fat due to enzyme inactivation.
- Nausea & vomiting: May be triggered by ulcer pain or gastric outlet obstruction.
Systemic symptoms
- Weight loss: Due to malabsorption and reduced appetite.
- Heartburn & gastro‑esophageal reflux: Excess acid irritates the esophagus.
- Fatigue: Secondary to anemia from chronic bleeding ulcers.
Symptoms related to the tumor itself
- Abdominal mass or vague fullness: Large gastrinomas can be palpable or cause a feeling of pressure.
- Metastatic signs: If the tumor spreads (commonly to the liver or lymph nodes), patients may develop jaundice, abdominal swelling, or bone pain.
Causes and Risk Factors
ZES results from the unregulated production of gastrin by neuroendocrine cells. The underlying causes can be divided into sporadic (non‑hereditary) and hereditary forms.
Genetic causes
- Multiple Endocrine Neoplasia type 1 (MEN‑1): Mutations in the MEN1 tumor suppressor gene predispose to gastrinomas, parathyroid, and pituitary tumors. ~20‑30% of ZES patients have MEN‑1.3
- Familial isolated gastrinoma syndrome: Rare autosomal‑dominant inheritance without other MEN‑1 features.
Acquired causes
- Sporadic gastrinomas: The majority of cases arise de novo, without a known genetic mutation.
- Chronic atrophic gastritis: Rarely leads to hypergastrinemia, but the pattern differs from ZES.
Risk factors
- Family history of MEN‑1 or gastrinoma.
- Age 30‑60 (peak incidence).
- Male sex (slight predominance).
- History of pancreatic or duodenal neuroendocrine tumors.
Diagnosis
Diagnosis relies on clinical suspicion, biochemical testing, and imaging to locate the tumor.
Biochemical tests
- Fasting serum gastrin level: A level > 1,000 pg/mL (≥10 × upper limit of normal) is highly suggestive, especially when gastric pH < 2.0.
- Secretin stimulation test: In ZES, gastrin paradoxically rises ≥ 120 pg/mL after intravenous secretin (0.4 U/kg). This is the most specific test.4
- Gastric pH measurement: Persistent acidity (pH < 2) despite high gastrin confirms hypersecretory state.
Imaging studies
- Multiphasic contrast‑enhanced CT or MRI: Detects primary gastrinoma and metastases.
- Somatostatin receptor scintigraphy (Octreoscan) or ^68Ga‑DOTATATE PET/CT: Highly sensitive for neuroendocrine tumors, especially small (< 1 cm) lesions.
- Endoscopic ultrasound (EUS): Useful for small pancreatic or duodenal lesions and for guiding fine‑needle aspiration.
- Selective arterial secretagogue injection (SASI) test: Rare, invasive test used when non‑invasive imaging fails.
Pathology
If a lesion is surgically removed, histology confirms a well‑differentiated neuroendocrine tumor (WHO grade 1–2) that stains positive for gastrin, chromogranin A, and synaptophysin.
Treatment Options
Management aims to control acid hypersecretion, remove or reduce tumor burden, and monitor for recurrence.
Acid‑suppression therapy (first line)
- Proton pump inhibitors (PPIs): High‑dose omeprazole, esomeprazole, or pantoprazole (typically 60‑120 mg/day) are required to keep gastric pH > 3.5
- H2‑receptor antagonists: May be added if PPIs are insufficient, but they are rarely adequate alone.
- Monitoring: Serum gastrin levels should be re‑checked after 1–2 weeks of PPI therapy to confirm suppression.
Surgical interventions
- Curative resection: Preferred for localized gastrinomas (< 2 cm) without metastasis. Typical procedures include segmental duodenal resection, pancreas‑sparing distal pancreatectomy, or enucleation.
- Debulking surgery: For metastatic disease, removal of > 90% of tumor bulk can improve symptoms and reduce gastrin output.
- Liver metastasis management: Options include hepatic resection, radiofrequency ablation, or transarterial chemoembolization (TACE).
Medical therapy for tumor control
- Somatostatin analogues (SSA): Octreotide or lanreotide bind somatostatin receptors, inhibiting gastrin release and tumor growth. Typical doses: octreotide LAR 30 mg IM every 4 weeks.
- Targeted therapy: Everolimus (mTOR inhibitor) and sunitinib (tyrosine‑kinase inhibitor) are approved for progressive, well‑differentiated pancreatic NETs; they may be used in ZES when SSA fails.
- Chemotherapy: Reserved for high‑grade or rapidly progressive disease; regimens often include streptozocin, 5‑FU, or capecitabine‑temozolomide.
Other supportive measures
- Calcium and vitamin D supplementation if MEN‑1‑associated hyperparathyroidism is present.
- Pancreatic enzyme replacement therapy for malabsorption.
- Regular bone density testing if chronic acid suppression or MEN‑1 leads to decreased calcium absorption.
Living with Zollinger‑Ellison Syndrome (Gastric NET)
Long‑term management combines medication adherence, nutrition, monitoring, and psychosocial support.
Medication adherence
- Take PPIs exactly as prescribed—missing doses often leads to breakthrough ulcers.
- Set reminders for monthly SSA injections or refill dates.
- Report new symptoms promptly (e.g., sudden abdominal pain, changes in stool).
Dietary & lifestyle tips
- Small, frequent meals: Reduces acid load.
- Avoid trigger foods: Caffeine, alcohol, spicy foods, and high‑fat meals can worsen reflux.
- Stay hydrated: Helps prevent constipation from reduced gastric motility.
- Low‑fat diet or enzyme supplements: Improves fat absorption when diarrhea is severe.
- Quit smoking – it impairs ulcer healing.
Monitoring schedule
| Test | Frequency | Purpose |
|---|---|---|
| Fasting gastrin level | Every 6‑12 months (or after medication change) | Assess tumor activity |
| Endoscopy | Every 1‑2 years or if symptoms change | Detect new ulcers or tumor growth |
| Cross‑sectional imaging (CT/MRI) | Annually, or sooner if symptoms worsen | Surveillance for metastasis |
| Bone density (DEXA) | Every 2‑3 years | Screen for osteoporosis (PPI use & MEN‑1) |
Psychosocial support
- Join rare‑disease or NET support groups (e.g., NET Patient Foundation).
- Consider counseling to cope with chronic illness stress.
- Discuss family planning; genetic counseling is advisable for patients with MEN‑1.
Prevention
Because most gastrinomas arise sporadically, primary prevention is limited. However, risk can be reduced by:
- Genetic counseling and testing for families with known MEN‑1 mutations.
- Avoiding chronic use of acid‑stimulating medications (e.g., H2 blockers discontinuation) only under physician guidance.
- Routine health check‑ups for individuals with MEN‑1 to detect tumors early.
Complications
If untreated or inadequately controlled, ZES can lead to serious health problems:
- Perforated ulcer: Can cause acute abdomen and peritonitis.
- Gastrointestinal bleeding: Chronic bleeding leads to iron‑deficiency anemia.
- Severe malabsorption: Resulting in weight loss, electrolyte imbalances, and vitamin deficiencies.
- Secondary pancreatic insufficiency: Due to enzyme inactivation.
- Metastatic disease: Liver, lymph nodes, or bone metastases diminish survival; 5‑year survival drops from > 90% (localized) to ≈ 50% (metastatic).6
- Gastric carcinoid tumors: Chronic hypergastrinemia can stimulate enterochromaffin‑like cells, producing gastric NET type 1.
When to Seek Emergency Care
Call 911 or go to the nearest emergency department if you experience any of the following:
- Sudden, severe abdominal pain that does not improve with medication.
- Vomiting blood (hematemesis) or black, tarry stools (melena).
- Rapid heart rate, dizziness, or fainting – possible signs of massive bleeding.
- Sudden inability to pass stool or gas with worsening abdominal distention – possible perforation.
- High fever (> 101 °F/38.3 °C) with abdominal pain – may indicate infection of a perforated ulcer.
These signs require immediate evaluation to prevent life‑threatening complications.
Sources:
1. Mayo Clinic. Zollinger‑Ellison syndrome. https://www.mayoclinic.org
2. Centers for Disease Control and Prevention. Rare Diseases: Zollinger‑Ellison syndrome. https://www.cdc.gov
3. National Institutes of Health. Multiple Endocrine Neoplasia. https://www.nih.gov
4. Cleveland Clinic. Zollinger‑Ellison Syndrome. https://my.clevelandclinic.org
5. Mayo Clinic. Zollinger‑Ellison syndrome: Treatment. https://www.mayoclinic.org
6. Modlin IM, et al. “Management of neuroendocrine tumors.” Nat Rev Clin Oncol. 2020;17:439‑456. PMCID: PMC6898266