PTH and secondary hyperparathyroidism: Studies with rapid intraoperative PTH measurement in secondary hyperparathyroidism demonstrated a stepwise decrease in circulating iPTH corresponding to sequential gland resection12, 21; and those findings together with a higher incidence of supernumerary/ectopic parathyroid glands in renal hyperparathyroidism7, 8, point to IO-PTH measurement as an interesting tool in an attempt to avoid surgical failure.