This study demonstrates that there is a number of different patient (gender, age, and thyrotoxicosis <10 years before surgery) and surgical (number of PGs found observed surgery, decreased Ca and iCa before surgery, PTH on day one following surgery, and ligation of the trunk of the left and right inferior thyroid artery) risk factors predictive of the development of hypocalcemia following TT. Here, PTH is linked to Hypocalcemia.