The majority are sporadic but may also occur as part of the autosomal dominantly inherited syndrome Multiple Endocrine Neoplasia type 1, which is caused by inactivation of the tumour suppressor gene Menin located on chromosome 11q13 and associated with tumours of the anterior pituitary, parathyroids, and pancreas. Here, MEN1 is linked to multiple endocrine neoplasia type 1.