Familial multiple endocrine neoplasia type 1 (MEN1), familial hypocalciuric (or familial benign) hypercalcemia (FHH), hyperparathyroidism jaw tumor syndrome (HPT-JT), other causes of familial isolated hyperparathyroidism (FIH), and pseudohypoparathyroidism (PHP) are disorders of metabolism that are generally inherited in an autosomal dominant fashion. MEN1 is characterized by overgrowth and hyperfunction of the parathyroids, anterior pituitary and gastrointestinal endocrine tissue. MEN1, p15, p18, p21, and p27 are identified genes for MEN 1- like states. FHH is characterized by a usually benign syndrome sometimes mistaken for typical primary hyperparathyroidism, which may result in unnecessary and unsuccessful parathyroid surgery. The CASR gene for the calcium-sensing receptor of the parathyroid cell is mutated in of most FHH kindreds;a minority of kindreds with FHH have mutation of the GA11 or AP2S gene. HPT-JT is a distinctive subtype of familial isolated hyperparathyroidism that has combinations of parathyroid adenoma, parathyroid cancer, jaw tumor, uterus tumor, kidney tumor and kidney cysts. It is caused by mutation of the HRPT2 gene. PHP is characterized by parathyroid hormone resistance, and one form is associated with mutations in the gene encoding the stimulatory G protein. We are continuing to collect blood and tissue samples from affected and unaffected members of kindreds with known or suspected MEN1, FHH, HPT-JT, FIH, PHP, and related disorders for the purpose of genetic analysis and gene identification. In most cases, the procurement of specimens will be at an off-site location. Samples will be processed for extraction of DNA and RNA.