Background:Microwave ablation has a great potential to treat primary hyperparathyroidism; but its predictors and the therapeutic efficiency are not clear enough and so the more investigations are required. Aim:The purpose of this study was to explore safety and predictors of the MWA efficacy in patients with primary hyperparathyroidism (PHPT) induced by parathyroid adenoma. Methods: Patients with PHPT treated with MWA were included in this study. Depending on the treatment efficacy, patients divided into two groups as response and no response group. Possible predictors as age, gender, Parathyroid adenoma volume, baseline levels of calcium (Ca), phosphorous (P), alkaline phosphate (ALP), vitamin D and location of parathyroid adenoma and the instrumental parameters which are microwave ablation time and power were compared between two groups. The resulting possible predictors the MWA efficacy exhibiting statistically significant difference was investigated by using logistic regression. Results: Thirty-two patients participated into predictor analysis for MWA efficacy. Comparison of the values of response and no response groups in terms possible predictors revealed only the baseline Ca level as the potential predictor of the efficacy of MWA (P <0.05). Further logistic regression results showed the baseline Ca level as insignificant to construct a mathematical model to predict the efficacy of MWA (P = 0.071). Furthermore, a significant difference in time differences was observed after 1 day of the MWA treatments in the levels of Ca, P, and PHT except than ALP, those of which was 30 days later (P <0.001). Later on, the difference stayed steady until the end of follow up. Conclusions:MWA is an effective and safe therapy for in patients with PHPT caused by parathyroid adenoma. Baseline Ca level has been found as potential but detailed investigations revealed none of the explored factors as predictive for the assessed patients. Keywords:Primary hyperparathyroidism, microwave ablation, predictor, efficacy