Classification of Hypoparathyroid Disorders.

The term hypoparathyroidism encompasses a huge group of disorders all characterized by an abnormal mineral homeostasis determined by inadequate secretion of parathyroid hormone. Postsurgical hypoparathyroidism is a complication of neck surgery (thyroidectomy, parathyroidectomy, lymph node, and cancer neck dissection), closely related to the extent of the surgical procedure and the experience of the surgeon. If lasting more than 6 months it is defined as chronic hypoparathyroidism, requiring life-long replacement therapy with active vitamin D metabolites. All the other forms of nonsurgical hypoparathyroidism, previously referred to as idiopathic hypoparathyroidism, have several causes, the majority of them genetic, which can be grouped into 3 main categories: disorder of parathyroid development, disorders of parathyroid function, and acquired damage to the parathyroids. Hypoparathyroidism can manifest as the sole disease in an individual (isolated hypoparathyroidism) or be associated with other manifestations within complex syndromes (syndromic hypoparathyroidism). Functional hypoparathyroidism, which may be caused by magnesium disturbances, has always to be ruled out before commencing the genetic diagnostic workup in nonsurgical forms. The search for signs of autoimmunity can drive the diagnosis towards an autoimmune pathogenesis of the disease, since a routine assessment of parathyroid autoantibodies is neither available nor specific.