The reduction of VDR in renal hyperparathyroidism was first reported by Korkor, who found that VDR levels in hypertrophic parathyroid glands in patients with CKD were substantially lower than those in transplant patients, especially when compared with adenomas in patients with primary hyperparathyroidism (PHPT) (Korkor, 1987). Here, VDR is linked to primary hyperparathyroidism.