Normocalcemic primary hyperparathyroidism — «new era» in diagnosis of an old disease

Abstract

During the last century, primary hyperparathyroidism (PHPT) passed from the category of rare severe diseases to a common endocrine disorder with a prevalence of mild forms. Over the last 10—20 years, widespread screening for osteoporosis has led to the «new era» in diagnosis of PHPT when patients are diagnosed at the stage of an isolated elevated parathyroid hormone with stable normal serum calcium levels and the absence of secondary causes of hyperparathyroidism. This phenomenon was called normocalcemic primary hyperparathyroidism (nPHPT); according to the literature data, its prevalence varies from 0.4 to 16.7% due to the lack of unified diagnostic criteria. The clinical picture and natural history of the disease are poorly explored, and it is still unclear if nPHPT is a separate disease entity or if it is an early stage of hypercalcemic PHPT. A number of studies have shown that complications of nPHPT (osteoporosis and urolithiasis) are similar to those of the symptomatic form of PHPT despite stable normocalcemia. However, these patients were often referred to specialized metabolic centers due to a decrease in the bone mass or nephrolithiasis, therefore the rate of complications in them may be overestimated. There are also controversial data on an increased risk of cardiovascular diseases due to metabolic disorders in this pathology. As a new clinical nosology, normocalcemic PHPT was first officially recognized at the Third International Workshop on Management of Asymptomatic PHPT in 2008, but there have been yet no common recommendations for its treatment. Some studies have shown a response to medical therapy and improved indicators of bone mineral density after parathyroidectomy in these patients. According to the experts of the Fourth International Workshop in 2014, nPHPT remains one of the key topics for further research.