PHEX and hyperparathyroidism: However, it should be taken into account that disturbance of the PTH secretion circadian rhythm has been reported among XLHR patients, which increase in nocturnal pulses [38], In addition, animal models of XLHR showed hyperparathyroidism in the absence of treatment [39], and abundant levels of PHEX mRNA were observed in the parathyroid gland of two XLH patients [40].