'Multiple endocrine neoplasia' or MEN is a medical expression for a grouping of distinct clinical patterns (a syndrome). The presence of any one tumor type does not automatically have a patient labelled as MEN, but a search of the other at-risk areas is usually undertaken anyway. 
MEN syndromes are inherited as autosomal dominant disorders. Medullary carcinoma of the thyroid may occur as an autosomal dominant in the absence of other features. 

MEN type 1 

  1. Parathyroid hyperplasia/tumour causing hyperparathyroidism. 

  2. Islet cell tumour causing hypoglycaemia (insulinoma) and Zollinger-Ellison syndrome (gastrinoma). 

  3. Pituitary adenoma which may cause pituitary hormone excess . 
    

The next two MEN syndrome types have their basis in molecular genetics. Individuals can be tested for this genetic disorder reliably even when asymptomatic patients. The mutation is in the 'ret' oncogene.

MEN type 2A 

  1. Medullary carcinoma of thyroid which is associated with increased calcitonin secretion. A test for elevated calcitonin should be done after pentagastrin injection and calcium infusion, to ensure that all affected patients are detected. 

  2. Pheochromocytoma 

  3. Parathyroid hyperplasia/tumour causing hyperparathyroidism. 
    

MEN type 2B

  1. Phaeochromocytoma 

  2. Medullary carcinoma of thyroid which is associated with increased calcitonin secretion. A test for elevated calcitonin should be done after pentagastrin injection and calcium infusion, to ensure that all affected patients are detected. 

  3. Mucosal neuromas which are usually situated in the gastrointestinal tract. 

  4. Marfanoid habitus