Endocrine System >
Multiple Endocrine Neoplasia

“In MEN syndromes there are functioning hormone-producing tumours in multiple organs with three subtypes: MEN 1 (Wemer syndrome), MEN 2A (Sipple syndrome) and MEN 2B”

Aetiology
  • MEN1 gene is a tumour suppressor gene which can cause an altered menin protein expression if mutated
  • MEN 2A and MEN 2B are caused by a mutated RET proto-oncogeneà elevated tyrosine kinase activity
Pathophysiology
  • MEN 1
    • Primary hyperparathyroidism (90%, most ↑ ­Ca)
    • Pancreas endocrine tumours (70%) such as gastrinoma and insulinoma or glucagonomas
    • Pituitary prolactinoma (50%)
    • GH secreting tumour
    • Carcinoid tumour
  • MEN 2A
    • Medullary Thyroid Carcinoma (95-100%)
    • Pheochromocytoma (50%)
    • Parathyroid hyperplasia
  • MEN 2B
    • Similar to MEN 2A plus mucosal neuromas and Marfanoid appearance but no hyperparathyroidism
Clinical Presentation
  • MEN 1
    • Hyperparathyroidism → ↑ Ca, bone abnormalities, weak, tired, thirsty, dehydrated but polyuric, abdominal pain.
    • Gastrinoma → Z-E syndrome, diarrhoea, upper abdominal pain due to ulcers.
    • Insulinoma → fasting hypoglycaemia with Whipple’s triad.
    • Glucagonomas → migrating rash, glossitis, cheilitis, anaemia, wt loss.
    • Carcinoid tumour → flushing, diarrhoea, bronchospasm
  • MEN 2A
    • Palpable neck mass, hypertension, episodic sweating, diarrhoea, elevated BP and HR in Pheochromocytoma
  • MEN 2B
    • Mucosal neuromas → bumps on lips, cheeks tongue glottis, eyelids and visible corneal nerves.
    • Marfanoid habitus → high arched palate, pectus excavatum, bilateral pescavus and scoliosis
Investigations
  • Genetic screening for RET mutations.
    • If mutations are identified, also screen family members at risk.
  • Serum calcium and PTH levels.
  • Screen for different hormones associated with potential MEN tumours (e.g fasting gastrin in gastrinomas).
  • DEXA scan and urinary tract imaging in hypercalcaemia to evaluate BMD.
Management
  • Parathyroidectomy to control hypercalcaemia.
  • Surgical removal of tumours with symptomatic treatment relating to the specific endocrine glands affected
Complications
  • Constant surveillance to identify any development of an additional tumour.
  • Associated with neurofibromatosis, Von Hippel- Lindau syndrome, Peutz- Jeghers syndrome and Carney complex.
  • Overall MEN1 has a reduced life expectancy and the outlook is dependent on which tumours a patient develops

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