**Abstract**

Hyperparathyroidism (HPT) is a clinical condition caused by the increase of parathyroid hormone (PTH) synthesis by the parathyroid glands. PTH has a central and fundamental role in the control of calcium and phosphorus homeostasis. Its action on the kidney, bone, and, indirectly, intestinal cells implies a rapid increase in extracellular calcium flow. This clinical condition may be due to an intrinsic parathyroid disorder or secondary to an imbalance of calcium metabolism in patients with systemic diseases, such as chronic renal failure. The treatment of hyperparathyroidism may be clinical, with the control of calcium, phosphorus, and PTH levels, or surgical, depending on the various forms presented. The purpose of the chapter is to discuss the types of hyperparathyroidism, their relationship with phosphorus and mainly calcium metabolism, as well as the main forms of diagnosis and treatment.

**Keywords:** hyperparathyroidism, calcium, bone diseases, kidney diseases, parathyroid hormone
