MEN1 and tumor of parathyroid gland: Interestingly, only a few germline mutations of MEN1 have been specifically associated to parathyroid tumors, including P325L (P320L in isoform 2), which is predicted to significantly decrease the protein stability of menin by targeting the protein for degradation [41], and D423N (D418N in isoform 2), whose molecular consequence is still unknown [40].