The intensity of parathyroid fluorescence that occurs after intravenous injection of indocyanine green during the performance of a total thyroidectomy correlates with postoperative parathyroid function and could be used as a diagnostic marker of postoperative hypoparathyroidism and hypocalcemia.

The main objective of the study is to compare the intensity of parathyroid fluorescence among patients who present post-thyroidectomy hypocalcemia with that of patients who do not have it. Therefore, the following points will be studied:

• To study the correlation between parathyroid vascularization (intraoperative fluorescence intensity) and postoperative glandular function (serum calcium and parathormone levels).
• To compare the surgeon's subjective assessment of parathyroid fluorescence in the groups of patients with and without postoperative hypocalcemia.
• To compare the objective assessment of parathyroid fluorescence, by using specific computer software developed ad hoc, in the groups of patients with and without postoperative hypocalcemia.

Inclusion Criteria:

• Patients who are going to undergo total thyroidectomy, with or without cervical lymph node dissection.
• Visualization of 2 or more parathyroid glands during the surgical act.
• Normal renal and hepatic functions.
• Absence of a history of hypersensitivity reactions to iodine or indocyanine green.
• Able to understand the nature and protocol of the study and its procedures
• Willingness to participate with the subsequent signing of informed consent.

Exclusion Criteria:

• Age <18 years
• Hepatic or renal insufficiency
• Hypersensitivity to iodine or to indocyanine green.
• Pregnancy or lactation
• Inability to understand the nature and procedures of the study.
• Patients with known preoperative hyperparathyroidism.