MEN1 and parathyroid gland adenoma: In sporadic adenoma, the most common somatic alteration is inactivation of MEN1. This is caused by loss of heterozygosity (LOH) due to large deletions or genetic recombination at 11q13 (where MEN1 is located) found in ~ 35% of all parathyroid adenoma and/or MEN1 inactivating mutations found in up to ~ 20% of cases [105].