There are two types of multiple endocrine neoplasia. They are MEN1 and MEN2. Although their names are similar, they are separate conditions. This information is about MEN1.
Your body is made up of tiny building blocks called cells. Inside every cell is a set of genes. These genes are the instructions the cell needs to work normally. Sometimes, the structure inside a gene is permanently changed, so the gene no longer gives the correct instructions. This change is called a gene mutation.
People with multiple endocrine neoplasia type 1 (MEN1) are born with a mutation in the MEN1 gene. Normally, this gene helps stop tumours developing. If the gene has a mutation, it may not do this job and certain types of tumour are more likely to develop.
Tumours can develop at any age. About 4 in 10 people with MEN1 (40%) develop a tumour by the time they are 20. About 8 in 10 people (80%) develop a tumour by the age of 50.