MEN1 and multiple endocrine neoplasia type 1: According to the 2012 Clinical Practice Guidelines for Multiple Endocrine Neoplasia Type 1,3 biochemical screening for pituitary tumors for individuals at high risk of MEN1 (i.e., mutation carriers) should include assessment of plasma prolactin and IGF-1 levels annually, in addition to MRI or computed tomography (CT) of the pituitary gland every 1–3 years.