Multiple Endocrine Neoplasia (MEN)

• Inheritance – autosomal dominant, typically high penetrance.
• Core types – MEN1, MEN2 (MEN2A, MEN2B, FMTC), and MEN4. [2]
• First manifestation often appears in young adulthood, but some tumors occur in childhood (especially MEN2-related medullary thyroid carcinoma). [3]
• Genes involved – MEN1 (menin), RET (MEN2), and CDKN1B (p27, MEN4). [1] [3] [5]

• Cancer risk – varies by subtype but includes high risk of medullary thyroid carcinoma (MEN2) and pancreatic neuroendocrine tumors (MEN1). [3] [2]
• Liver link – MEN itself does not start in the liver, but neuroendocrine tumors (especially pancreatic/duodenal NETs) can metastasize to the liver and occasionally lead to consideration of liver transplantation. [7]
• Multidisciplinary care – requires close collaboration between endocrinology, genetics, oncology, and (for some patients) the transplant team.

• Indication for transplant – for example, metastatic pancreatic neuroendocrine tumors (NETs) in a patient with MEN1 may lead to consideration of liver transplant when disease is liver-dominant and meets strict oncologic criteria. [7]
• Peri-operative risk – undiagnosed pheochromocytoma in MEN2 can cause severe hypertensive crises during anesthesia and transplant surgery. [3] [4]
• Long-term cancer risk – immunosuppression after transplant may increase the risk of new or recurrent endocrine and non-endocrine tumors, so MEN patients usually need even more structured cancer surveillance.

• Metabolic and bone health – longstanding hyperparathyroidism in MEN1/MEN4 increases risk of osteoporosis, bone pain, and fractures, which may worsen with chronic liver disease and post-transplant steroids. [2]
• Adrenal and pituitary function – pituitary tumors or prior pituitary surgery/radiation can result in adrenal insufficiency, hypothyroidism, or hypogonadism that require meticulous hormone replacement before major surgery. [2]
• Family implications – transplant evaluation is often an opportunity to recognize an inherited MEN syndrome in the family and refer relatives for genetic counseling and testing. [3]

1. Clinical and Genetic Assessment

• Detailed personal and family history of:
  Parathyroid disease Pituitary tumors Pancreatic/duodenal NETs Medullary thyroid carcinoma Pheochromocytoma
• Review prior operative notes and pathology (e.g., thyroidectomy, parathyroidectomy, pituitary surgery, NET resections).
• Genetic testing or review of existing results:
  • MEN1 gene for MEN1 families. [1]
  • RET sequencing for MEN2 families. [3]
  • CDKN1B for suspected MEN4 when MEN1 testing is negative but phenotype is MEN1-like. [5]

2. Biochemical and Imaging Work-up

• Calcium & PTH – screen for hyperparathyroidism and treat significant hypercalcemia prior to transplant. [2]
• Pituitary axis – morning cortisol ± ACTH stimulation, TSH/free T4, prolactin, IGF-1, plus MRI if clinically indicated. [2]
• Gastro-entero-pancreatic NETs – fasting gastrin, insulin, glucagon, or other hormones as guided by symptoms, plus cross-sectional imaging (contrast CT/MRI) ± functional imaging and endoscopic ultrasound as available. [2]
• Pheochromocytoma screening in MEN2 or unexplained hypertension – plasma free metanephrines or 24-hr urinary fractionated metanephrines, followed by adrenal imaging if positive. [3] [4]

Peri-Operative Endocrine Management

• Adrenal function – ensure adequate glucocorticoid coverage in patients with pituitary disease or prior steroid therapy; adjust peri-operative stress-dose steroids accordingly. [2]
• Calcium management – correct significant hypercalcemia or hypocalcemia (e.g., after parathyroidectomy) before surgery; monitor closely post-operatively as fluid shifts and transfusions may alter levels. [2]
• Pheochromocytoma – if present, definitive treatment (surgery with pre-operative alpha-blockade) should usually occur before transplant; if previously resected, confirm biochemical cure. [3] [4]
• Glucose and hormonal control – secretory NETs (insulinoma, gastrinoma, VIPoma) require careful peri-operative glucose and acid–base management. [2]

Post-Transplant Issues in MEN

• Immunosuppression strategy – aim for the lowest effective immunosuppressive exposure; some centers consider tailoring regimens in patients with strong oncologic risk, although evidence is evolving.
• Surveillance for MEN-related tumors – transplant does not eliminate predisposition to new endocrine tumors; continue MEN-specific surveillance (parathyroid, pituitary, thyroid/RET-positive, NET imaging) based on subtype. [2]
• Surveillance for NET recurrence – when transplant was performed for neuroendocrine liver metastases, long-term imaging follow-up is essential; 5-year survival can be favorable in carefully selected patients, but recurrence is not uncommon. [7] [8]
• General post-transplant cancer screening – skin exams, age-appropriate colonoscopy, breast/prostate screening, and HPV-related cancer prevention take on added importance.

Core Elements of Follow-up

• Structured endocrine visits – at least yearly visits with an endocrinologist familiar with MEN, with bloodwork and imaging guided by syndrome subtype and prior tumor history. [2]
• Transplant clinic – regular monitoring of liver function, immunosuppression levels, renal function, and infection risk.
• Bone health – DEXA scans, calcium/vitamin D optimization, and other osteoporosis therapies as indicated, given the combined effects of MEN-related hyperparathyroidism, prior steroids, and chronic liver disease. [2]

Self-Advocacy for Patients and Families

• Keep a simple written or electronic summary of:
  MEN subtype Gene mutation Major surgeries Current hormones
  and share it with every new clinician.
• Clarify which relatives qualify for genetic testing or surveillance and encourage them to seek counseling in a genetics clinic. [3]
• Discuss pregnancy planning, contraception, and family-building options (including pre-implantation genetic testing where appropriate) with both endocrinology and transplant teams. [3]