<p>The aim of this study was to evaluate the critical role of IOPTH assay in the success of&#xa0;Minimally Invasive Parathyroidectomy (MIP). This retrospective study was carried out in 42 patients diagnosed with Primary hyperparathyroidism and underwent Parathyroidectomy in a teritiary care hospital. Preoperative localization of the adenoma was performed by high-resolution neck ultrasound (US) and 99Tc labelled Sestamibi (MIBI)scan. In patients where localization could not be done by the above methods, 4DCT scanning of the neck was carried out. Suspected adenoma was dissected and removed by focused exposure. Intact parathormone estimations were obtained at pre-incision as baseline and 10 minutes after excision of the adenoma in all patients. Frozen section examination of the excised gland was also undertaken. Surgical endpoint was reached when the Intra-Operative prarathormone (IOPTH) level fell by 50% compared to the pre-incision level. All patients were followed up for 6 months for any recurrence of hyperparathyroidism by estimating the serum calcium. The mean preoperative serum calcium was 12.09+1.68 mg/dL with a mean serum PTH level of 110.73+ 313.90pg/mL. US localization was positive in 28 cases [65.17%]. MIBI scan was positive in 32 cases [74.42%]. In 4 cases where pre-operative radiological localization was not clear, 4-DCT was done. The end point of surgery in all cases was decided by 50% reduction in IOPTH compared to the pre-operative levels. The mean serum calcium at 6months was 8.83(+1.75) mg/dL. Frozen section biopsy of the excised tissue revealed single parathyroid adenoma in 38 patients, double adenomas in two patients and parathyroid gland hyperplasia in two patients. IOPTH estimation is a critical adjunct in ensuring surgical success in MIP. It facilitates a less invasive, safer procedure with high long term cure rates.</p>