Normocalcemic hyperparathyroidism is the mild-early clinical stage of frank primary form

Normocalcemic primary hyperpararathyroidism (NHPT) represents a recent nosologic entity, ranging from the 0.4 to 3.1% of all the primary hyperparathyroidism (PHPT) but the natural history and its evolution has not been elucidated  yet. In a recent study published on the Journal of Clinical Endocrinology and Metabolism, the ECTS Academy members Andrea Palermo and Nicola Napoli compared the clinical, biochemical and radiological profile of three cohorts of NHPT, PHPT and healthy subjects. They found that the biochemical phenotype of NHPTs was intermediate between PHPTs and controls with the serum calcium level normal, the PTH value similarly higher as the PHPTs, and the serum phosphorus lower than controls. They also weighted several bone parameters and showed how the bone phenotype of the NHPTs was not dissimilar from the controls, with no significant bone mineral density impairment, nor an increased risk of vertebral fractures. They concluded that, from a clinical point of view, NHPT could be considered and classified as a mildly-early form of PHPT, and thus needs to be carefully followed up to determine its progression.

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