The goal of this randomized clinical trial is to learn if there are any added benefits of using near-infrared autofluorescence (NIRAF) probe-based imaging system (the PTeye) for intraoperative identification of parathyroid glands (PGs) during thyroid surgery in comparison to visual identification of PGs by the surgeon's naked eyes without PTeye. The main questions it aims to answer are: * Is number of PGs identified intraoperatively and preserved in situ larger in thyroid operations with PTeye versus surgeon's naked eyes without PTeye? * Is number of patients with undetectable or low parathormone serum level on postoperative day 1 fewer in thyroid operations with PTeye versus surgeon's naked eyes without PTeye? * Is number of patients requiring substitution therapy with calcium and vitamin D analogue fewer after thyroid operations with PTeye versus surgeon's naked eyes without PTeye in a short-term (\< 6 weeks) and/or in a long-term (at 6 months) follow-up? * Is numer of inadvertenly removed and reimplanted PGs fewer in thyroid operations with PTeye versus surgeon's naked eyes without PTeye? * Is number of frozen sections fewer in thyroid operations with PTeye versus surgeon's naked eyes without PTeye? * Is number of PGs identified by pathologist in the surgical specimen fewer in in thyroid operations with PTeye versus surgeon's naked eyes without PTeye? * Is number of patients with symptomatic hypoparathyroidism within 30 days of the operation fewer in thyroid operations with PTeye versus surgeon's naked eyes without PTeye? The hypothesis explored in this study is that use of PTeye in comparison to the surgeon's naked eyes may be beneficial for intraoperative identification and preservation of PGs in thyroid surgery leading to reduced risk of postoperative hypoparathyroidism. A prospective, randomized study with 2 arms: use of PTeye vs. visual identification of PGs without PTeye (n=77 patients, each). The primary outcome measure is number of intraoperatively identified PGs with use of PTeye vs without it.