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Zollinger‑Ellison Syndrome (Gastrinoma) Associated with Neuroendocrine Tumor

Overview

Zollinger‑Ellison syndrome (ZES) is a rare disorder caused by one or more gastrin‑secreting neuroendocrine tumors (NETs), most often called gastrinomas. The excess gastrin stimulates the stomach to produce large amounts of gastric acid, leading to severe peptic ulcer disease, diarrhea, and malabsorption.

• Who it affects: Adults aged 30–60 years, with a slight male predominance (≈55 %). Up to 25 % of cases occur in children or adolescents, usually in the context of a hereditary syndrome.
• Prevalence: Approximately 1–3 cases per million people worldwide. The annual incidence is estimated at 0.1–0.3 per 100,000 population.<sup>1</sup>
• Relation to neuroendocrine tumors: Gastrinomas are a subset of pancreatic or duodenal NETs. About 80 % arise in the duodenum, 20 % in the pancreas, and <2 % are ectopic.

The condition can occur sporadically or as part of the inherited multiple endocrine neoplasia type 1 (MEN‑1) syndrome, which also includes parathyroid and pituitary tumors.

Symptoms

Symptoms result from excessive gastric acid and from the mass effect of the tumor. They may be intermittent at first and become more constant as disease progresses.

• Recurrent or refractory peptic ulcers – often multiple, distal (beyond the duodenum), and unresponsive to standard therapy.
• Abdominal pain – burning or gnawing pain that may improve with meals (ulcer pain) or worsen after eating (acid reflux).
• Heartburn and gastro‑esophageal reflux disease (GERD) – due to high acid load.
• Chronic diarrhea – usually watery, due to acid inactivation of pancreatic enzymes and injury to the intestinal mucosa.
• Steatorrhea (fatty stools) – malabsorption of fat from pancreatic enzyme inactivation.
• Weight loss – secondary to malabsorption, diarrhea, and decreased oral intake because of pain.
• Nausea & vomiting – may be triggered by ulcer complications.
• GI bleeding – melena or hematemesis from ulcer erosion.
• Upper abdominal fullness or a palpable mass – more common when the tumor is large or metastatic.
• Symptoms of MEN‑1 (if present) – hypercalcemia (stones, bone pain), pituitary headaches or visual changes.

Causes and Risk Factors

Primary cause

ZES is caused by gastrin‑producing neuroendocrine tumors. These tumors arise from enterochromaffin‑like (ECL) cells in the duodenum or pancreas.

Genetic risk factors

• Multiple Endocrine Neoplasia type 1 (MEN‑1): Germ‑line mutations in the MEN1 tumor suppressor gene account for ~20–25 % of ZES cases.<sup>2</sup>
• Familial gastrinoma: Rare autosomal‑dominant inheritance without other MEN‑1 features.

Non‑genetic risk factors

• Age 30‑60 (peak incidence)
• Male sex (modest excess)
• History of chronic gastritis or H. pylori infection does not cause ZES but may exacerbate ulcer symptoms.

Pathophysiology snapshot

Gastrin binds to CCK‑B receptors on parietal cells → massive H⁺ secretion → low gastric pH (<2). The acidic environment overwhelms protective mechanisms, erodes the mucosa and inactivates pancreatic enzymes, producing the characteristic clinical picture.

Diagnosis

Because symptoms overlap with common ulcer disease, a high index of suspicion is essential.

Laboratory tests

• Fasting serum gastrin: Levels > 1000 pg/mL (normal < 100 pg/mL) are highly suggestive, especially when gastric pH < 2.<sup>3</sup>
• Secretin stimulation test: Intravenous secretin normally inhibits gastrin; in gastrinomas it paradoxically raises gastrin > 120 pg/mL after administration.
• Chromogranin A (CgA): A general NET marker; elevated in 70‑80 % of gastrinomas.
• Calcium & parathyroid hormone (PTH): To screen for MEN‑1.

Imaging studies

• Endoscopic ultrasound (EUS): High‑resolution detection of small (<1 cm) duodenal or pancreatic lesions.
• Multiphasic contrast CT or MRI abdomen: Evaluates tumor size, local invasion, and liver metastases.
• Somatostatin receptor scintigraphy (SRS) – Octreoscan® or Ga‑68 DOTATATE PET/CT: Detects somatostatin‑receptor‑positive NETs and guides surgical planning.
• Selective arterial secretin stimulation test (SASST): Invasive but useful when non‑invasive tests are inconclusive.

Endoscopic evaluation

Upper endoscopy (EGD) identifies multiple ulcers, confirms high acidity, and allows biopsy to exclude H. pylori or malignancy unrelated to gastrinoma.

Treatment Options

Management aims to control acid hypersecretion, remove or control the tumor, and monitor for recurrence.

Acid‑suppression therapy

• High‑dose proton‑pump inhibitors (PPIs): Omeprazole 40–80 mg daily or equivalent; most patients achieve symptom control.
• H2‑receptor antagonists: Used as adjuncts when PPIs are insufficient.

Long‑term PPI use is generally safe but requires monitoring for hypomagnesemia, B12 deficiency, and osteoporosis.

Surgical management

• Curative resection: Enucleation or pancreaticoduodenectomy for localized tumors without metastasis.
• Debulking surgery: Reduces tumor burden when metastases are present; may improve symptom control.
• Liver-directed therapies: Radiofrequency ablation, hepatic artery embolization, or peptide‑receptor radionuclide therapy (PRRT) for liver metastases.

Medical therapies for unresectable or metastatic disease

• Somatostatin analogues (e.g., octreotide, lanreotide): Inhibit gastrin release and may shrink tumors.
• Targeted agents: Everolimus (mTOR inhibitor) and sunitinib (tyrosine‑kinase inhibitor) approved for advanced pancreatic NETs.
• Chemotherapy: Streptozocin‑based regimens; limited efficacy but used in aggressive disease.
• Peptide‑receptor radionuclide therapy (PRRT): ^177Lu‑DOTATATE delivers radiation directly to somatostatin‑receptor‑positive cells. Shown to improve progression‑free survival in NETs (NETTER‑1 trial).<sup>4</sup>

Lifestyle & supportive measures

• Small, frequent meals; avoid foods that trigger reflux.
• Stay hydrated, especially if diarrhea is prominent.
• Calcium‑ and vitamin D‑supplementation if on long‑term PPIs.
• Regular bone density screening (DXA) for osteoporosis risk.

Living with Zollinger‑Ellison Syndrome (gastrinoma) Associated with Neuroendocrine Tumor

Daily management tips

• Medication adherence: Take PPIs exactly as prescribed; never skip doses.
• Monitor symptoms: Keep a diary of abdominal pain, stool frequency, and any bleeding.
• Nutrition:
  • Choose low‑fat, low‑fiber foods if steatorrhea is problematic.
  • Consider medium‑chain triglyceride (MCT) oils, which are easier to absorb.
• Hydration: Replace fluids and electrolytes lost through diarrhea (oral rehydration solutions are useful).
• Regular follow‑up:
  • Every 3–6 months: gastrin level, endoscopy, imaging if indicated.
  • Annual: chromogranin A, liver function tests, and bone density.
• Support networks: Join NET patient groups (e.g., NET Cancer Support Network) for emotional coping and latest research updates.

Psychosocial considerations

Chronic disease can cause anxiety and depression. Early referral to counseling or a mental‑health professional is recommended, especially if coping with MEN‑1‑related tumors.

Prevention

Because most gastrinomas are sporadic, primary prevention is limited. However, risk reduction strategies include:

• Genetic counseling and testing for families with known MEN‑1 or familial gastrinoma mutations.
• Regular surveillance (annual fasting gastrin, imaging) for at‑risk individuals.
• Eradication of Helicobacter pylori infection to lower background ulcer risk (does not prevent ZES but reduces additive damage).

Complications

If untreated or inadequately controlled, ZES can lead to serious health issues:

• Perforated duodenal or gastric ulcer – surgical emergency.
• Severe GI bleeding – may require endoscopic hemostasis or transfusion.
• Malnutrition & weight loss – due to chronic diarrhea and malabsorption.
• Osteoporosis – chronic acid suppression and malabsorption of calcium/vitamin D.
• Liver metastases – develop in 60‑80 % of patients over time; worsen prognosis.
• Carcinoid crisis (rare): sudden release of hormone‑like substances causing flushing, hypotension, bronchospasm.
• Progression to neuroendocrine carcinoma – high‑grade tumors have poorer survival.

When to Seek Emergency Care

References

1. Mayo Clinic. “Zollinger‑Ellison syndrome.” Updated 2023. https://www.mayoclinic.org
2. American Association of Endocrine Surgeons. “MEN1 and Gastrinomas.” 2022 guideline.
3. NIH National Institute of Diabetes and Digestive and Kidney Diseases. “Zollinger‑Ellison syndrome.” 2022. https://www.niddk.nih.gov
4. Strosberg J, et al. “Phase 3 Trial of ^177Lu-DOTATATE for Midgut Neuroendocrine Tumors (NETTER‑1).” *NEJM* 2017;376:125‑135.

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