CCND1 and parathyroid hyperplasia: Rearrangements involving the PTH gene locus in 20–40% parathyroid adenoma patients identified cyclin D1 overexpression, suggesting that overexpression of PRAD1/cyclin D1 is one of the genetic abnormalities responsible for tumorigenesis in sporadic primary parathyroid adenomas contributing to parathyroid hyperplasia in humans [71,72].