```html

Zollinger‑Ellison‑Like Syndrome (Gastrin‑Producing Neuroendocrine Tumors)

Overview

Zollinger‑Ellison‑like syndrome (ZELS) is a rare condition caused by gastrin‑producing neuroendocrine tumors (NETs) that arise outside the pancreas or duodenum, most often in the stomach, jejunum, or lymph nodes. These tumors secrete large amounts of gastrin, a hormone that stimulates stomach acid production. The resulting hyperacidity leads to severe peptic ulcer disease, gastro‑esophageal reflux, and malabsorption.

Although the classic “Zollinger‑Ellison syndrome” (ZES) is linked to gastrin‑producing tumors (gastrinomas) of the duodenum or pancreas, the term “Zollinger‑Ellison‑like syndrome” is used when similar hormonal activity is identified in NETs that do not fit the classic anatomic locations or occur as part of multiple endocrine neoplasia type 1 (MEN‑1).

Who is affected? ZELS can occur at any age but most patients are diagnosed between **40 and 70 years**. Men and women are affected equally, though a slight male predominance is noted in some series (55 % male). Approximately **5–10 %** of all gastrin‑producing NETs present as a Zollinger‑Ellison‑like picture rather than classic ZES.<sup>1</sup>

Prevalence: Gastrin‑producing NETs are very rare, with an estimated incidence of **0.5–2 cases per million persons per year**.<sup>2</sup> Because ZELS represents a subset of these tumors, the true population prevalence is less than 1 per million.

Symptoms

Symptoms result from excess gastric acid and from the mass effect of the tumor. They can be intermittent at first and may mimic common gastrointestinal disorders.

• Refractory peptic ulcer disease – ulcer pain that does not improve with standard proton‑pump inhibitor (PPI) therapy.
• Epigastric or upper abdominal pain – often worsened by meals, described as burning or gnawing.
• Gastro‑esophageal reflux disease (GERD) – heartburn, sour taste, or nighttime cough.
• Diarrhea or steatorrhea – chronic watery stools or fatty stools due to acid‑induced inactivation of pancreatic enzymes.
• Weight loss – secondary to malabsorption and reduced oral intake because of pain.
• Nausea and vomiting – sometimes with blood (hematemesis) if ulcers erode vessels.
• Upper gastrointestinal bleeding – melena (black tarry stools) or hematemesis.
• Abdominal bloating and early satiety – especially when the tumor is large.
• Fatigue and anemia – from chronic blood loss.
• New‑onset gallstones – caused by altered bile composition due to high acid load.
• MEN‑1 associated features – hyperparathyroidism, pituitary adenomas, or other endocrine tumors when ZELS occurs as part of MEN‑1.

Causes and Risk Factors

Primary cause

The root cause is the development of a **neuroendocrine tumor that secretes gastrin**. These tumors arise from the enterochromaffin‑like (ECL) cells of the gastrointestinal tract. The exact molecular trigger for sporadic gastrinomas is not fully understood, but several mechanisms have been identified:

• Genetic mutations – loss‑of‑function mutations in the tumor suppressor gene MEN1 (chromosome 11q13) are seen in up to 25 % of gastrinomas, especially those linked to MEN‑1 syndrome.<sup>3</sup>
• Chromosomal alterations – gains in chromosome 5q and losses in 11q are reported in sporadic NETs.
• Chronic hypergastrinemia – long‑standing conditions that raise gastrin (e.g., chronic atrophic gastritis) may predispose to ECL cell hyperplasia and neoplasia.

Risk factors

• Family history of MEN‑1 or other endocrine neoplasias.
• Known germline MEN1 mutation.
• Long‑term use of proton‑pump inhibitors (PPIs) – controversial, but chronic suppression can lead to hypergastrinemia that may promote ECL proliferation.
• Previous gastric surgery (e.g., Billroth II) that alters acid feedback.
• Age >40 years (peak incidence).

Diagnosis

Because the symptoms overlap with common ulcer disease, a high index of suspicion is necessary, especially when ulcers are multiple, recurrent, or refractory to therapy.

Laboratory tests

• Fasting serum gastrin – levels > 1000 pg/mL (normal < 100 pg/mL) are highly suggestive. Levels > 10× the upper limit with a gastric pH < 2 support the diagnosis.
• Secretin stimulation test – administration of secretin paradoxically raises gastrin in gastrinomas; a rise ≥ 120 pg/mL after 2 minutes is diagnostic.<sup>4</sup>
• Baseline gastric pH measurement – confirms hyperacidity.
• Routine blood work – CBC (to detect anemia), liver panel, renal function, and fasting glucose (NETs can cause hypoglycemia).

Imaging studies

1. Endoscopic ultrasound (EUS) – high‑resolution detection of small gastric or duodenal lesions.
2. Somatostatin receptor imaging (e.g., 68Ga‑DOTATATE PET/CT) – identifies primary tumor and metastases because most NETs overexpress somatostatin receptors.
3. CT or MRI of the abdomen – for anatomic localization; arterial phase imaging improves detection of hypervascular NETs.
4. Selective arterial calcium stimulation – used when non‑invasive imaging is inconclusive; calcium injection into arteries causes a localized gastrin surge.

Pathology

If a lesion is resected, histology confirms a well‑differentiated neuroendocrine tumor (WHO grade 1 or 2) with immunohistochemical positivity for gastrin, chromogranin A, and synaptophysin.

Treatment Options

Management aims to (1) control acid hypersecretion, (2) eradicate or control tumor growth, and (3) address any metastatic disease.

Acid‑control medications

• High‑dose proton‑pump inhibitors (PPIs) – omeprazole 40–80 mg daily or equivalent are first‑line; most patients require lifelong therapy.
• H2‑receptor antagonists – famotidine or ranitidine can be added for breakthrough symptoms.
• Potassium‑competitive acid blockers (P‑CABs) – e.g., vonoprazan (available in some countries) provide rapid, potent acid suppression.

Surgical approaches

• Curative resection – en‑bloc removal of the primary gastrinoma and any regional lymph nodes is preferred for localized disease. Laparoscopic techniques are increasingly used.
• Debulking surgery – for metastatic disease, reducing tumor burden can improve symptoms and hormone control.
• Pancreaticoduodenectomy (Whipple) – considered when the tumor invades the head of the pancreas or duodenum.

Medical therapies for tumor control

• Somatostatin analogues – octreotide or lanreotide bind somatostatin receptors, decreasing gastrin secretion and slowing tumor growth. Long‑acting depot formulations are standard.
• Targeted therapy – everolimus (mTOR inhibitor) and sunitinib (tyrosine‑kinase inhibitor) are approved for advanced pancreatic NETs and can be used off‑label for gastrinomas.
• Peptide receptor radionuclide therapy (PRRT) – ^177Lu‑DOTATATE delivers radiotherapy directly to somatostatin‑receptor‑positive cells; improves progression‑free survival in metastatic NETs.
• Chemotherapy – limited role; reserved for high‑grade or poorly differentiated NETs (e.g., streptozocin‑based regimens).

Liver‑directed treatments (for metastases)

• Radiofrequency ablation or microwave ablation.
• Transarterial embolization (TAE) or chemo‑embolization (TACE).
• Surgical hepatic resection when feasible.

Lifestyle and supportive measures

• Small, frequent meals to reduce acid load.
• Avoidance of alcohol, caffeine, spicy foods, and nicotine – all stimulate acid secretion.
• Calcium‑vitamin D supplementation if PPIs cause hypocalcemia.
• Vaccination against Helicobacter pylori if infection is present.

Living with Zollinger‑Ellison‑Like Syndrome (gastrin‑producing NETs)

Long‑term management focuses on symptom control, monitoring for disease progression, and maintaining quality of life.

• Medication adherence – never skip PPIs; an acid breakthrough can rapidly cause ulcer bleeding.
• Regular follow‑up – serum gastrin and imaging (usually annually) to detect recurrence or metastasis.
• Nutrition – work with a dietitian to ensure adequate protein, calories, and micronutrients; consider medium‑chain triglyceride (MCT) oils if fat malabsorption is severe.
• Bone health – chronic PPI use may reduce calcium absorption; DEXA scanning every 2–3 years is advisable.
• Psychosocial support – joining NET patient groups (e.g., NETpatient.org) can help address anxiety and coping strategies.

Prevention

Because most gastrin‑producing NETs are sporadic, primary prevention is limited. However, risk can be reduced by:

• Screening individuals with a known MEN1 mutation with periodic fasting gastrin levels and abdominal imaging.
• Testing and treating H. pylori infection promptly.
• Using the lowest effective dose of PPIs and re‑evaluating the need for chronic therapy under medical supervision.
• Avoiding tobacco and excessive alcohol, which exacerbate ulcer disease.

Complications

If left untreated or inadequately controlled, ZELS can lead to serious complications:

• Perforated peptic ulcer – can cause peritonitis and requires emergency surgery.
• Severe gastrointestinal bleeding – may need endoscopic hemostasis, blood transfusion, or surgery.
• Duodenal or gastric strictures – from chronic ulcer scarring, leading to obstruction.
• Malabsorption and nutritional deficiency – especially fat‑soluble vitamins (A, D, E, K).
• Metastatic disease – liver, lymph nodes, or bone metastases occur in 30–50 % of gastrinomas at diagnosis.
• Osteoporosis – chronic acid suppression and malabsorption contribute to bone loss.
• MEN‑1 related endocrine tumors – hyperparathyroidism, pituitary adenoma, and others may develop.

When to Seek Emergency Care

---

Sources:
1. NIH National Cancer Institute. “Neuroendocrine Tumors of the Stomach and Duodenum.” 2023.
2. Yao JC, et al. “One Hundred Years of Neuroendocrine Tumors.” J Clin Oncol. 2022;40(15):1655‑1664.
3. Brandi ML, et al. “Multiple Endocrine Neoplasia Type 1.” Lancet Diabetes Endocrinol. 2021;9(9):619‑632.
4. Jensen RT, et al. “Secretin Stimulation Test for Gastrinoma Diagnosis.” Gastroenterology. 2020;158(2):405‑410.
5. Mayo Clinic. “Gastrinoma (Zollinger‑Ellison Syndrome).” Updated 2023.
6. NCCN Guidelines Version 2.2024 – Neuroendocrine and Pancreatic Tumors.
7. WHO Classification of Tumours of the Digestive System, 5th Edition, 2024.

```