Parathyroid tumour development was also found to occur in >40% of the 32 conditional knockout mice, which comprised 15 Cdc73+/L/PTH-Cre mice (9 males and 6 females) and 17 Cdc73L/L/PTH-Cre mice (8 males and 9 females), but not in any of 20 Cdc73+/+/PTH-Cre mice (11 males and 9 females), aged 20–21 months of age. This evidence concerns the gene CDC73 and tumor of parathyroid gland.