Evaluation of Levothyroxine Replacement Therapy After Total Thyroidectomy Using a Smart Wristband

The goal of this observational study is to determine whether nighttime heart rate and heart rhythm data collected by a smart wristband can identify under- or over-replacement with levothyroxine before the routine 1-month thyroid function tests in adults who have undergone total thyroidectomy. After total thyroidectomy, patients usually start levothyroxine replacement therapy, and the dose is adjusted about 1 month later based on thyroid function tests. This study aims to determine whether changes in nighttime heart rate and heart rhythm can provide an earlier indication that the levothyroxine dose is too low or too high. The main questions it aims to answer are: Can nighttime heart rate and heart rhythm measured by a smart wristband identify under- or over-replacement with levothyroxine before routine thyroid function testing? How well do smart wristband measurements agree with thyroid function test results? Participants will: Wear a smart wristband after total thyroidectomy. Continue taking levothyroxine as prescribed by their physician. Undergo routine thyroid function testing approximately 1 month after surgery as part of standard clinical care. Allow researchers to compare smart wristband measurements with thyroid function test results to evaluate whether wearable data can provide an earlier indication of inadequate or excessive levothyroxine replacement.

Inclusion Criteria: Age 18 years or older. Undergoing total thyroidectomy at the Department of General Surgery, Yeditepe University Faculty of Medicine Hospital. Initiation of levothyroxine as part of routine postoperative clinical care. Willing and able to attend the routine 1-month postoperative thyroid function test follow-up visit. Willing and able to wear the Xiaomi Smart Band 10 throughout the study period. Able to provide written informed consent. Exclusion Criteria: History of cardiac arrhythmia. Current use of beta-blockers or other antiarrhythmic medications that may affect heart rate. History of heart failure or advanced cardiovascular disease. Diagnosed sleep disorders that may interfere with nighttime heart rate measurements. Pregnancy. Inability or unwillingness to wear the smart wristband as required. Missing clinical or laboratory data required for outcome assessment. Refusal to participate or withdrawal of informed consent.