To validate procedural success, intraoperative parathormone monitoring(ioPTHm) is crucial in parathyroid surgery.Although various centers employ different ioPTHm criteria, some patients exhibit suboptimal parathormone(PTH) reduction immediately postexcision, achieving desired levels upon subsequent measurement.This study aims to identify factors influencing these cases.

A prospective observational study(April 2021-August 2023) involved primary hyperparathyroidism patients undergoing focused parathyroidectomy. Successful ioPTHm was defined as a PTH measurement at 20 minutes postexcision, showing a decrease to the normal range or >50%.Patients with insufficient decrease had first-hour postexcision PTH levels measured. Demographic data, perioperative data, laboratory values, and follow-up data were recorded.

Over two years;87 females and 13 males(mean age:54.75) underwent surgery. In 97 patients with sufficient PTH decrease, the operation was successful. Three patients with inadequate decrease underwent a repeat test, with two achieving sufficient decrease, both having vitamin D deficiency. In one patient GFR was 43 ml/min/1,73m2 and surgery was terminated. During one-year follow-up, three patient exhibited persistence or recurrence: Two patients had a sufficient PTH decrease during their first surgery.In one patient, neither 20th-minute nor first-hour PTH values exhibited sufficient decrease.

We recommend accepting a >50% decrease or normalization of PTH at the 20th minute during ioPTHm for low recurrence and high success rates. Factors influencing PTH metabolism, such as vitamin D deficiency or chronic kidney failure, may be considered in cases of inadequate immediate decrease.In cases of certain preoperative localization and insufficient PTH decrease intraoperatively at 20 minutes postexcision, measuring PTH at the first hour can be suggested to avoid unnecessary exploration and complications.