Hyperparathyroidism 1, also known as familial isolated hyperparathyroidism, is related to multiple endocrine neoplasia, type i and hyperparathyroidism 2 with jaw tumors. An important gene associated with Hyperparathyroidism 1 is CDC73 (Cell Division Cycle 73). Affiliated tissues include kidney and bone, and related phenotypes are osteopenia and hypophosphatemia