Parathyroid glands are endodermal-derived organs responsible for the production of the parathyroid hormone (PTH), an essential regulator of calcium homeostasis. The role of the parathyroids in human diseases is almost exclusively related to its hyperfunction, mainly mediated via primary hyperparathyroidism, which is a relatively common disease and is the main cause of hypercalcemia in outpatients. This book discusses the development of parathyroid glands and c-cells; homeostasis, disease and indications for surgical treatment in the parathyroid glands; hyperfunction in the parathyroid glands; contemporary surgical management or primary hyperparathyroidism; and the role of parathyroid hormones in heart failure.