PLPPR4 and primary hyperparathyroidism: A total of among the 49 PHP1 patients (26 males, 23 females; 25.1 ± 10.8 years) as well as 64 primary hyperparathyroidism (PHPT) patients (13 males, 51 females; 55.5 ± 14.3 years) and 30 normal controls (14 males, 16 females; 26.3 ± 11.2 years) were included in this study (Table 1).