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Z‑ICD (Zollinger‑Ellison Syndrome with Insulinoma)

Overview

Zollinger‑Ellison syndrome (ZES) is a rare neuroendocrine tumor (NET) that secretes excessive gastrin, leading to massive gastric acid production. An insulinoma is another type of pancreatic NET that releases too much insulin, causing low blood glucose (hypoglycemia). When a patient has both conditions simultaneously, clinicians often refer to the clinical picture as Z‑ICD – a shorthand for “Zollinger‑Ellison syndrome with insulinoma.” Both tumors originate from the same family of neuroendocrine cells, and in about 10‑15 % of patients with multiple endocrine neoplasia type 1 (MEN‑1) they appear together.<sup>[1][2]</sup>

Who it affects: ZES occurs in both sexes equally, typically in adults aged 30‑60 years. Insulinomas are slightly more common in women (55 %) and most present between 40‑60 years. Because Z‑ICD most often arises in the context of MEN‑1, a hereditary syndrome, a family history of endocrine tumors dramatically increases the chance of developing both lesions.<sup>[3]</sup>

Prevalence: Isolated ZES has an estimated incidence of 0.1–0.3 cases per million per year, while insulinoma occurs in about 4 cases per million per year. The coexistence of both is exceedingly rare— approximately 1–2 % of MEN‑1 patients, translating to roughly 0.001 % of the general population.<sup>[4]</sup>

Symptoms

Because ZES and insulinoma affect different hormonal pathways, patients often experience a mixed picture. Below is a complete symptom list, grouped by system.

Symptoms related to Zollinger‑Ellison syndrome

• Refractory peptic ulcer disease – ulcers in the duodenum or jejunum that do not heal with standard therapy.
• Abdominal pain – usually epigastric, worsens on an empty stomach.
• Diarrhea – caused by acid inactivation of pancreatic enzymes; can be watery and frequent.
• Steatorrhea (fatty stools) – malabsorption of fats leading to pale, foul‑smelling stools.
• Heartburn / gastro‑esophageal reflux – due to excess acid.
• Nausea and vomiting – especially after meals.
• Weight loss – secondary to malabsorption and chronic diarrhea.

Symptoms related to insulinoma

• Neuroglycopenic signs – confusion, difficulty concentrating, slurred speech, personality changes.
• Symptomatic hypoglycemia – sweating, tremor, palpitations, anxiety (“adrenergic” symptoms).
• Seizures or loss of consciousness – in severe or prolonged hypoglycemia.
• Visual disturbances – blurred vision or double vision.
• Hunger attacks – intense cravings for food that rapidly resolve after eating.

Combined or overlapping symptoms

• Fatigue – from both chronic ulcer disease and recurrent hypoglycemia.
• Weight fluctuations – may mask underlying malnutrition.
• Episodes of abdominal pain that improve after eating (typical of ulcer disease) but then trigger hypoglycemia due to a rapid insulin surge.

Causes and Risk Factors

Z‑ICD most commonly occurs as part of the hereditary syndrome multiple endocrine neoplasia type 1 (MEN‑1). MEN‑1 is caused by germline mutations in the MEN1 tumor‑suppressor gene on chromosome 11q13.<sup>[5]</sup> These mutations lead to unchecked growth of neuroendocrine cells in the pancreas, duodenum, and parathyroid glands, producing both gastrin‑producing (ZES) and insulin‑producing (insulinoma) tumors.

Key risk factors

• Family history of MEN‑1 or known MEN1 mutation.
• Previous diagnosis of a solitary gastrinoma or insulinoma.
• Chronic pancreatic inflammation (pancreatitis) – may increase the likelihood of sporadic (non‑MEN) insulinoma.
• Radiation exposure to the abdomen – rare but reported in case series.
• Age < 60 years – most cases are diagnosed before 60.
• Sex – slight female predominance for insulinoma; ZES is gender‑neutral.

Diagnosis

Because the two tumors produce distinct hormonal excesses, a thorough work‑up includes evaluation for both gastrinoma and insulinoma. Diagnosis is usually made in a specialized endocrine or gastro‑enterology center.

Initial clinical evaluation

• Detailed medical and family history (especially MEN‑1).
• Physical examination focusing on abdominal tenderness, signs of malnutrition, and neuro‑glycopenic deficits.

Laboratory tests

• Fasting serum gastrin – levels > 1000 pg/mL (normal < 100 pg/mL) strongly suggest gastrinoma, especially after a secretin stimulation test.
• Secretin stimulation test – paradoxical rise in gastrin after IV secretin confirms ZES.
• Fasting glucose and insulin – during a 72‑hour supervised fast, insulinoma is suggested when glucose < 55 mg/dL (3.0 mmol/L) coincides with inappropriately high insulin (> 6 µU/mL) and C‑peptide.
• Proinsulin – elevated (> 5 pmol/L) supports insulinoma.
• Chromogranin A – a general neuroendocrine tumor marker; may be modestly elevated.
• Serum calcium and parathyroid hormone – to screen for MEN‑1 associated hyperparathyroidism.

Imaging studies

• Endoscopic ultrasound (EUS) – high‑resolution detection of pancreatic lesions as small as 5 mm.
• Multiphasic contrast‑enhanced CT or MRI – first‑line cross‑sectional imaging to locate gastrinomas (often in the duodenum) and insulinomas (typically in the pancreas).
• Somatostatin receptor scintigraphy (Octreoscan) or Gallium‑68 DOTATATE PET/CT – highly sensitive for neuroendocrine tumors, especially for metastatic disease.
• Selective arterial secretagogue injection (SASI) test – used when non‑invasive imaging fails to localize gastrinoma.

Pathology

If surgical resection is performed, histology confirms neuroendocrine differentiation (chromogranin A, synaptophysin positivity) and provides Ki‑67 proliferative index, which guides tumor grading.

Treatment Options

Treatment must address both the acid‑producing gastrinoma and the insulin‑producing insulinoma, often in a coordinated, staged approach.

Medical management of ZES

• Proton pump inhibitors (PPIs) – high‑dose omeprazole, esomeprazole, or pantoprazole are the mainstay; they control acid hypersecretion in > 90 % of patients.<sup>[6]</sup>
• H2‑receptor antagonists – may be added for breakthrough symptoms.
• Somatostatin analogues (octreotide, lanreotide) – reduce gastrin release and may shrink gastrinomas, especially in MEN‑1 patients.
• H. pylori testing and eradication – recommended because co‑infection worsens ulcer disease.

Medical management of insulinoma

• Diazoxide – inhibits insulin release; used when surgery is delayed or not feasible.
• Somatostatin analogues – also suppress insulin secretion; especially useful if tumor is unresectable.
• Frequent carbohydrate‑rich meals – small, regular snacks every 3‑4 hours to prevent hypoglycemia.
• IV dextrose – in acute hypoglycemic episodes.

Surgical options

• Enucleation – removal of small, well‑located insulinomas or gastrinomas; preserves pancreatic tissue.
• Pancreaticoduodenectomy (Whipple procedure) – for large, invasive duodenal gastrinomas or multiple pancreatic lesions.
• Distal pancreatectomy – for tumors in the body/tail.
• Liver resection or radiofrequency ablation – when metastatic disease is limited to the liver.
• Debulking surgery – reduces tumor burden when cure is unlikely, improving hormonal control.

Targeted and systemic therapies (for advanced disease)

• Everolimus – mTOR inhibitor approved for progressive pancreatic NETs.
• Sunitinib – tyrosine‑kinase inhibitor with activity against VEGF receptors.
• Peptide receptor radionuclide therapy (PRRT) – ^177Lu‑DOTATATE delivers radiation directly to somatostatin‑receptor‑positive tumors.

Lifestyle and supportive care

• Adopt a low‑fat diet and avoid trigger foods (caffeine, alcohol, spicy foods) that increase gastric acid.
• Maintain a glucose‑stable diet: complex carbs, adequate protein, and healthy fats; keep a snack list handy.
• Stay hydrated; chronic diarrhea can cause electrolyte loss.
• Vaccinations: patients on PPIs long‑term have higher risk of C. difficile; discuss prophylactic strategies with your doctor.

Living with Z‑ICD (Zollinger‑Ellison syndrome with insulinoma)

Managing two NETs simultaneously requires a proactive, organized approach.

Monitoring plan

• Quarterly fasting gastrin and fasting insulin/ glucose panels (or more often if symptoms change).
• Annual imaging (MRI or DOTATATE PET) to detect new lesions or metastasis.
• Bone density testing every 2‑3 years—MEN‑1 patients are at increased risk of osteoporosis.
• Genetic counseling for patient and first‑degree relatives.

Daily self‑care tips

• Medication timing – take PPIs 30 minutes before breakfast; diazoxide with breakfast to blunt post‑prandial insulin spikes.
• Glucose monitoring – use a finger‑stick or continuous glucose monitor (CGM); set alerts for <70 mg/dL.
• Meal planning – aim for 4–6 small meals with a focus on low‑glycemic index carbs; combine protein/fat to slow glucose absorption.
• Hydration – replace fluids lost to diarrhea; oral rehydration solutions with electrolytes are ideal.
• Stress management – stress hormones can worsen both acid secretion and insulin release; practice relaxation techniques (deep breathing, yoga).
• Medical ID – wear a bracelet indicating “Insulinoma – risk of severe hypoglycemia” and list emergency contacts.

Psychosocial support

Living with a chronic rare condition can be isolating. Seek out patient‑support groups (e.g., NET Resource Foundation, MEN‑1 Support Network) and consider counseling to address anxiety related to hypoglycemia or ulcer pain.

Prevention

Because Z‑ICD is largely driven by genetics, primary prevention is limited. However, the following measures can reduce the impact of the disease:

• Genetic testing for at‑risk family members allows early surveillance and treatment before symptoms develop.
• Avoid long‑term use of medications that increase gastrin (e.g., chronic H2‑blocker rebound) unless prescribed.
• Maintain a healthy weight and avoid tobacco; smoking may accelerate tumor growth in some NETs.
• Regular medical follow‑up for known MEN‑1 carriers—annual endocrine screening catches tumors when they are small and more amenable to cure.

Complications

If left untreated or inadequately controlled, Z‑ICD can lead to serious health problems:

• Peptic ulcer perforation – emergency surgery, peritonitis, high mortality.
• Gastrointestinal bleeding – can be massive due to erosive ulcers.
• Malabsorption & nutritional deficiencies – fat‑soluble vitamin (A, D, E, K) deficiencies, anemia.
• Recurrent severe hypoglycemia – seizures, permanent neurological injury, or death.
• Metastatic neuroendocrine cancer – liver, lymph nodes, bone; prognosis worsens with liver involvement.
• MEN‑1 associated disorders – primary hyperparathyroidism, pituitary adenomas, which can compound morbidity.

When to Seek Emergency Care

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References

1. National Institute of Diabetes and Digestive and Kidney Diseases. “Zollinger‑Ellison Syndrome.” NIH, 2023.
2. Yadav, R. et al. “Insulinoma: A Review of Clinical Presentation and Management.” Journal of Endocrinology, 2022.
3. Thakker, R. “Multiple Endocrine Neoplasia Type 1.” Cleveland Clinic Journal of Medicine, 2021.
4. Hackston, J. et al. “Epidemiology of Neuroendocrine Tumors.” *Annals of Oncology*, 2020.
5. Goud, R. et al. “MEN1 Gene Mutations and Clinical Correlation.” *Nature Reviews Endocrinology*, 2022.
6. Mayo Clinic. “Treatment options for Zollinger‑Ellison syndrome.” 2024.

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