What is Multiple Endocrine Neoplasia (MEN)?

These are a group of disorders where affected individuals develop tumours in two or more endocrine glands at the same time, making the affected glands overactive. With several endocrine systems being overactive, a diverse range of symptoms is seen. They are inherited disorders (inherited in an autosomal dominant pattern).

There are two main types of MEN syndrome:

MEN type 1 (Wermer's syndrome)

This was first described by Wermer in 1954. It is a rare disorder, affecting approximately 0.25% of the population. It affects all age groups, with cases reported from 5-81 years of age. Clinical symptoms have normally appeared by the fifth decade of life.

It is characterised by the co-existence of:

• Parathyroid tumours - 80-95% cases
• Pancreatic islet cell tumours (including gastrinomas, insulinomas, glucagonomas, VIPomas and PPomas) - 80% cases
• Anterior pituitary tumours (prolactin -, growth hormone- and ACTH-secreting tumours and non-functioning tumours) - 50-71% cases

More rarely tumours of the adrenal cortex, carcinoid tumours (special tumours, often arising in the gut - described in their own section) and lipomas (tumours of fat tissue) may also occur within MEN-1.

MEN type 2 (Sipple's syndrome)

This syndrome was first described by Sipple in 1961. It is less common than MEN 1, but again affects all age groups with cases reported from 2-60 years of age. Symptoms develop less readily than in MEN 1 with 40% of people with the gene remaining asymptomatic at 70 years of age.

It is divided into two further sub-classes:

MEN 2a

The most common variant of MEN 2. This is characterised by:

• Cancer of the medulla of the thyroid (medullary thyroid carcinoma, MTC) - almost 100%
• Phaeochromocytoma (tumour of the adrenal medulla) - 50%
• Parathyroid tumours - 40-80%

MEN2b

This has no parathyroid involvement and is characterised by:

• Medullary thyroid carcinoma
• Phaeochromocytoma
• Marfanoid habitus (a body shape seen in Marfan's syndrome, a connective tissues disorder, where individuals are very tall and thin with long limbs and digits)
• Mucosal neuromas (tumours of nervous tissue in the mucous membranes)
• Medullated corneal nerve fibres (nerves going to the cornea at the front of the eye become enlarged)
• Megacolon (grossly dilated large intestine due to problems with the nerves to the gut)

The syndrome can occur with the only manifestation being medullary thyroid carcinoma.