Can math make thyroid hormone therapy more precise?

Copied word for word from the study's registry entry, so the wording is the study team's rather than ours.

Inclusion Criteria: * Aged 18-65 years, inclusive, regardless of sex. * Able to fully understand the study and voluntarily sign the informed consent form. * Histologically or cytologically confirmed advanced or metastatic thyroid cancer, treatment-naïve, and requiring total or near-total thyroidectomy. * Eastern Cooperative Oncology Group (ECOG) performance status ≤2. * No clinically significant contraindications to surgery. * Body weight ≥50.0 kg for males and ≥45.0 kg for females, with a body mass index (BMI) of 19.0-26.0 kg/m², inclusive. * Able to maintain regular daily routines, communicate effectively with the investigator, comply with all study requirements, and adhere to scheduled study visits, treatment plans, and laboratory assessments. * Adequate baseline organ function at the screening visit, as demonstrated by local laboratory values meeting the protocol-specified eligibility requirements. Exclusion Criteria: * Thyroid cancer patients for whom the planned or completed thyroidectomy does not meet the criteria for total or near-total thyroidectomy. * Prior treatment for thyroid cancer, including surgery and/or pharmacological treatment. * Major surgery, including radiosurgery, or significant traumatic injury within 2 weeks prior to randomization. * History of another malignancy within 3 years prior to initiation of study treatment. * Known history of a positive human immunodeficiency virus (HIV) test. * Known active hepatitis B virus (HBV) or hepatitis C virus (HCV) infection; chronic or resolved HBV or HCV infection is permitted. * Congenital or acquired immunodeficiency. * History of clinically significant drug allergy or atopic allergic disease (e.g., asthma, urticaria, or eczematous dermatitis), or known hypersensitivity to Euthyrox (levothyroxine sodium) or any of its excipients. * Pregnant or breastfeeding females.