PTH and primary hyperparathyroidism: The resulting disorders share a constellation of inappropriately high PTH concentrations despite elevated serum calcium levels and are categorized into three groups based on genetic origin, time of onset and severity of clinical symptoms, namely familial hypocalciuric hypercalcemia (FHH), neonatal severe primary hyperparathyroidism (NSHPT), and neonatal hyperparathyroidism (NHPT) [2,3,4].