PHPT was the first clinical manifestation in 92 cases (63.45% of all MEN1 affected patients; 66.19% of PHPT cases); 25 of them were diagnosed with PHPT after symptoms of nephrocalcinosis and/or renal colic, while 67 were biochemically diagnosed in presence of elevated serum PTH and, in the great majority of cases (65), also hypercalcemia. This evidence concerns the gene MEN1 and hypercalcemia disease.