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.