Objective: To study the relationship of intraoperative parathormone (PTH) decrease levels with solitary parathyroid adenoma (SPA) weight, diameter, and volume of the adenoma in patients with primary hyperparathyroidism (PHPT). Method: Prospectively evaluation of consecutive patients undergoing parathyroidectomy (PTx) with the diagnosis of PHPT related to SPA. Perioperative biochemical parameters of patients; volume, weight and diameters of adenoma were recorded. Intraoperative PTH drop percentages were calculated. Adenoma diameter and volume were measured and calculated using preoperativ ultrasound. Adenoma was weighed intraoperatively by the surgeon. Results: Forty-five consecutive patients underwent PTx for a SPA between October 2018 and October 2019. There were 9 men and 36 women, with a mean age of 51 ± 14.94 years. A positive correlation was identified between the volume with the weight and maximum diameter of resected parathyroid glands (r = 0.613, p< 0.001; r = 0.871, p< 0.001, respectively). There was a positive correlation between volume and preoperative PTH levels, albeit a weak one (r = 0.334, p = 0.025). No significant relationship was found between adenoma volume and ioPTH drop rate (r = 0.088, p = 0.565). Conclusions: We have not been able to establish criteria based on correlation between PA volume and weight and the ioPTH drop rate that would allow us to make decisions on ending the parathyroidectomy and reducing persistent PHPT cases.