Factors Influencing Time to Decrease in Intraoperative Parathyroid Hormone (ioPTH) Levels in Patients Undergoing Focused Parathyroidectomy (FP).

The aim of this study was to evaluate potential factors affecting the time period in which a 50 per cent parathyroid hormone (PTH) drop is observed. Eight-seven patients undergoing focused parathyroidectomy between 2011 and 2015, whose PTH values dropped to within normal range, were grouped according to whether they required > or ≤15 minutes after gland excision to achieve a 50 per cent PTH. Groups were compared according to preoperative PTH, calcium, age, glomerular filtration rate, and adenoma weight. Lower preoperative and preincision PTH levels were associated with requiring >15 minutes to achieve a >50 per cent drop in ioPTH. Time to >50 per cent ioPTH drop did not affect cure rates at one year, though a >15 minutes requirement was associated with higher serum calcium levels (P = 0.015). Lower baseline PTH and preincision PTH levels are significantly associated with a >15 minutes postexcision time to achieve a >50 per cent drop in ioPTH. Future analyses are warranted to determine whether a longer postexcision time threshold before proceeding with four-gland exploration is warranted in patients with primary hyperparathyroidism and mildly elevated preoperative PTH.