Thyroidectomy is one of the most common operations performed worldwide by various surgeons whether general or endocrine surgeons. The rate of complications following thyroidectomy has been progressively decreasing yet it still carries significant morbidity if preoperative preparation and patient as well as procedure selection were not optimized. The aim of this study is to evaluate the reliability of perioperative parathyroid hormone measurement to predict post-total thyroidectomy hypocalcaemia.Our study was prospective non-randomized study done from November 2018 till September 2019 in Benha university hospital, general surgery department, Benha, Egypt. The study included 50 patients having thyroid disease for whom total thyroidectomy was indicated. From the study serum calcium concentrations have been the basis of identification of post-operative hypocalcaemia however this has been replaced by PTH levels being more sensitive and specific to the early prediction of hypocalcaemia. In the study a drop in postoperative PTH levels by more than 62% compared to preoperative level giving 75% Sensitivity, 84.21% Specificity, PPV 60% and NPV 91.43%. a drop in postoperative PTH levels by more than 62% may serve as a sensitive and specific indicator of hypocalcemia with high overall accuracy and this will help in selecting patients for early discharge after total thyroidectomy.