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Zollinger‑Ellison Syndrome (Gastrinoma)

Overview

Zollinger‑Ellison syndrome (ZES) is a rare disorder in which one or more tumors called gastrinomas secrete excessive amounts of the hormone gastrin. Gastrin stimulates the stomach lining to produce large volumes of gastric acid, leading to severe peptic ulcer disease, gastro‑intestinal (GI) bleeding, and malabsorption.

• Prevalence: Approximately 1–3 cases per million people worldwide, making it one of the least common endocrine tumors of the GI tract.<sup>[1] Mayo Clinic</sup>
• Typical age of onset: 30–60 years, though cases in children and adolescents have been reported.
• Gender: Slight male predominance (about 55 % male).
• Association with MEN‑1: Up to 25 % of patients have Multiple Endocrine Neoplasia type 1, a hereditary syndrome involving the parathyroid, pituitary, and pancreatic islet cells.<sup>[2] NIH</sup>

Symptoms

Because excess acid affects many parts of the digestive system, ZES produces a broad spectrum of symptoms. The intensity often correlates with the amount of gastrin secreted.

Gastro‑intestinal symptoms

• Refractory peptic ulcers: Ulcers that persist despite standard therapy, frequently located in the duodenum, jejunum, or even the distal ileum.
• Upper abdominal (epigastric) pain: Crampy, burning pain that may improve after eating (due to buffering of acid) or worsen with acid‑rich meals.
• Diarrhea: Occurs in 30–50 % of patients; acidic chyme inactivates pancreatic enzymes and damages the intestinal mucosa, leading to steatorrhea (fatty stools).
• Nausea & vomiting: May be triggered by ulcer pain or by rapid gastric emptying.
• Gastro‑intestinal bleeding: Melena (black tarry stools) or hematemesis (vomiting blood) from ulcer erosion.

Systemic symptoms

• Weight loss: Due to malabsorption, chronic diarrhea, and reduced appetite.
• Fatigue & anemia: Chronic blood loss and iron deficiency.
• Electrolyte disturbances: Low potassium or magnesium secondary to persistent diarrhea.

Signs suggesting MEN‑1 association

• Hyperparathyroidism (high calcium, kidney stones)
• Pituitary adenoma (headaches, visual changes, hormonal abnormalities)

Causes and Risk Factors

Primary cause

ZES is caused by a gastrin‑producing neuroendocrine tumor (NET) of the pancreas or duodenum. In >90 % of cases the tumor is well‑differentiated and slowly growing, but a minority are aggressive (poorly differentiated) and can metastasize to the liver, lymph nodes, or distant sites.

Genetic risk factors

• Multiple Endocrine Neoplasia type 1 (MEN‑1): Autosomal dominant mutation in the MEN1 tumor suppressor gene. Carriers have a 3–5 % lifetime chance of developing a gastrinoma.
• Familial gastrinoma syndrome: Rare inherited gastrin‑producing tumors not linked to MEN‑1.

Other risk factors

• Age 30–60 years (peak incidence)
• Male sex (slightly higher risk)
• History of other pancreatic neuroendocrine tumors
• Chronic H. pylori infection or long‑term NSAID use do not cause ZES but can mask or exacerbate ulcer symptoms.

Diagnosis

Because symptoms mimic common ulcer disease, a high index of suspicion is required, especially when ulcers are multiple, recurrent, or located beyond the duodenum.

Initial laboratory evaluation

• Fasting serum gastrin level: Value > 1,000 pg/mL (or > 10× upper limit) in the presence of low gastric pH strongly suggests ZES. Levels between 150–1,000 pg/mL require further testing.
• Secretin stimulation test: Intravenous secretin paradoxically raises gastrin > 120 pg/mL in ZES (normal response is a decrease). This test improves diagnostic accuracy when fasting gastrin is inconclusive.<sup>[3] Cleveland Clinic</sup>
• Acid output measurement (Basal Acid Output, BAO): Elevated (> 15 mEq/h) supports the diagnosis.

Imaging studies

1. Endoscopic ultrasound (EUS): Sensitive for tumors < 1 cm in the pancreas or duodenum.
2. Multiphasic contrast‑enhanced CT or MRI: Identifies primary tumor size, local invasion, and metastases.
3. Somatostatin receptor scintigraphy (Octreoscan) or ^68Ga‑DOTATATE PET/CT: Detects both primary lesions and distant disease due to high expression of somatostatin receptors on NETs.<sup>[4] WHO</sup>
4. Selective arterial secretin stimulation test (SASS): Rarely used; involves sampling gastrin from hepatic veins after selective arterial secretin injection to localize tumor.

Histopathology

If a lesion is resected, pathology confirms a neuroendocrine tumor with immunostaining for gastrin, chromogranin A, and synaptophysin. Ki‑67 proliferative index guides grading (G1‑G3) and prognosis.

Treatment Options

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

Acid‑suppression therapy (core of initial treatment)

• High‑dose proton pump inhibitors (PPIs): Omeprazole 60–120 mg/day, esomeprazole 40–80 mg/day, or equivalent. PPIs normalize gastric pH within 24–48 h and heal ulcers in > 90 % of patients.<sup>[5] Mayo Clinic</sup>
• Histamine‑2 receptor antagonists (H2RAs): Less effective than PPIs; may be used as adjuncts.
• Long‑term PPI therapy is usually required indefinitely unless the tumor is cured surgically.

Surgical management

• Curative resection: For solitary tumors < 2 cm without metastasis, pancreaticoduodenectomy (Whipple), distal pancreatectomy, or local duodenal excision may achieve cure in 60–80 % of cases.
• Debulking surgery: If extensive disease, removing ≥ 90 % of tumor burden can reduce gastrin output and improve symptoms.
• Liver metastasis treatment: Options include hepatic resection, radiofrequency ablation, or trans‑arterial embolization.

Medical therapies for tumor control

1. Somatostatin analogues: Octreotide or lanreotide bind somatostatin receptors, decreasing gastrin secretion and slowing tumor growth. Doses: octreotide LAR 30 mg IM every 28 days.
2. Targeted therapy: Everolimus (mTOR inhibitor) and sunitinib (tyrosine‑kinase inhibitor) are FDA‑approved for advanced pancreatic NETs; they improve progression‑free survival.<sup>[6] NIH</sup>
3. Peptide‑Receptor Radionuclide Therapy (PRRT): ^177Lu‑DOTATATE delivers radiation directly to somatostatin‑receptor‑positive tumors; shown to cause tumor shrinkage in > 30 % of ZES patients with metastatic disease.<sup>[7] NEJM</sup>
4. Chemotherapy: Reserved for high‑grade (G3) neuroendocrine carcinomas; regimens such as cisplatin/etoposide.

Lifestyle & supportive measures

• Small, frequent meals to lessen acid load.
• Avoidance of alcohol, caffeine, nicotine, and NSAIDs, which exacerbate ulcer formation.
• Supplementation with fat‑soluble vitamins (A, D, E, K) if steatorrhea is present.
• Regular bone‑density testing if long‑term PPI use is anticipated (risk of decreased calcium absorption).

Living with Zollinger‑Ellison Syndrome (gastrinoma)

Daily management tips

1. Medication adherence: Take PPIs exactly as prescribed; missing doses can cause rebound acid hypersecretion.
2. Track symptoms: Keep a diary of pain episodes, stool consistency, and any bleeding. Promptly report new or worsening signs to your gastroenterologist.
3. Nutrition:
   • Consume a balanced diet rich in protein and complex carbohydrates.
   • If diarrhea is problematic, use medium‑chain triglyceride (MCT) oil supplements, which are absorbed without pancreatic enzymes.
4. Regular follow‑up:
   • Serum gastrin and chromogranin A levels every 6–12 months.
   • Imaging (CT/MRI or ^68Ga‑DOTATATE PET) annually, or sooner if symptoms flare.
5. Vaccinations: Patients on somatostatin analogues or everolimus have modest immunosuppression; stay up to date with flu, COVID‑19, and pneumococcal vaccines.
6. Psychosocial support: Chronic disease can cause anxiety or depression. Consider counseling, support groups, or referral to a mental‑health professional.

Prevention

Because most gastrinomas arise sporadically, primary prevention is limited. However, risk can be lowered by:

• Genetic counseling and periodic screening (fasting gastrin, endoscopic ultrasound) for individuals with a known MEN1 mutation.
• Early detection of ulcer disease: patients with recurrent or atypical ulcers should be evaluated for ZES rather than solely treated with PPIs.
• Maintaining a healthy weight and avoiding smoking, which decrease overall gastrointestinal cancer risk.

Complications

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

• Multiple, refractory peptic ulcers – increased risk of perforation, hemorrhage, and need for emergency surgery.
• Gastro‑intestinal bleeding – may cause iron‑deficiency anemia or require transfusion.
• Severe malabsorption – chronic diarrhea and steatorrhea lead to weight loss, electrolyte abnormalities, and deficiencies of fat‑soluble vitamins.
• Metastatic disease – up to 50 % of patients develop liver metastases over time; distant spread worsens prognosis.
• Peptic ulcer–induced perforation – a surgical emergency associated with high mortality if not promptly treated.
• Osteoporosis – long‑term PPI use and malabsorption of calcium/vitamin D increase fracture risk.

When to Seek Emergency Care

References

1. Mayo Clinic. “Zollinger‑Ellison syndrome.” Updated 2023. https://www.mayoclinic.org/diseases-conditions/zollinger-ellison-syndrome
2. National Institutes of Health (NIH). “Multiple endocrine neoplasia type 1.” 2022. https://www.nih.gov/condition/multiple-endocrine-neoplasia-type-1
3. Cleveland Clinic. “Secretin Stimulation Test for Gastrinoma.” 2021. https://my.clevelandclinic.org/health/diagnostics/17039-secretin-stimulation-test
4. World Health Organization (WHO). “Neuroendocrine Tumors of the Digestive System.” 2020. https://www.who.int/news-room/fact-sheets/detail/neuroendocrine-tumours
5. Mayo Clinic. “Proton pump inhibitors: What you need to know.” 2022. https://www.mayoclinic.org/diseases-conditions/acid-reflux/in-depth/ppis/art-20488770
6. National Cancer Institute (NCI). “Targeted Therapy for Pancreatic Neuroendocrine Tumors.” 2023. https://www.cancer.gov/types/pancreatic/patient/pancreatic-neuroendocrine-treatment-pdq
7. Strosberg J. et al. “Phase 3 Trial of ^177Lu‑DOTATATE for Mid‑gut Neuroendocrine Tumors.” *New England Journal of Medicine*, 2021. https://doi.org/10.1056/NEJMoa1911419

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