Increased urinary ca excretion above 400 is considered an indication for doing parathyroidectomy

A) Increased urinary ca excretion above 400 is considered an indication for doing parathyroidectomy in asymptomatic cases . But sir why is there increased urinary Ca excretion in Primary hyperparathyroidism ?? ( As PTH cause tubular reabsorption from kidneys )

B) mc cause of mortality in primary hyperparathyroidism would be :

The normal physiology of calcium metabolism is complex and depends on many factors such as renal function, diet, and age. When this normal metabolism is disrupted, it can acutely lead to hypercalcemia, which causes an increase in urinary calcium excretion through mediation of the calcium sensing receptor (CaSR) in the kidney. Hypercalciuria has been used as a diagnostic marker and indicator for parathyroidectomy in patients with primary hyperparathyroidism (PHPT). Thank you.