Rigorous selection was performed, following not only the traditionally required criteria [normocalcemia (in this study, total and ionized calcium); vitamin D sufficiency (defined as concentrations > 30 ng/dL); absence of chronic kidney disease, and no use of interfering drugs (2)], but also excluding other factors that can alter PTH in apparently healthy individuals (e.g., hypercalciuria, conditions of malabsorption, hyperphosphatemia, hypomagnesemia), which were not considered in previous studies (2,18,19). This evidence concerns the gene PTH and familial primary hypomagnesemia.