CASR and hyperparathyroidism: Hyperparathyroidism also hyperstimulates CaSR and accelerates the rate of vitamin D conversion to its active form (1,25-(OH)2 vitamin D), thus patients with PHPT are at greater risk of vitamin D insufficiency than eucalcaemic individuals [22], consequently, Ca accumulates in the kidneys and results in the formation of renal calculi and if left untreated, can lead to kidney injury.