This observational study aims to evaluate the performance of a software-based medical device, Glandy HYPER, in detecting the thyrotoxic state in patients with hyperthyroidism. The device utilizes heart rate data collected from commercially available wearable devices and compares it with thyroid function test results. The study will enroll patients diagnosed with Graves' disease, monitoring their heart rate during sleep and correlating these measurements with free T4 levels obtained through serial blood testing. No investigational device output will be disclosed to participants, and the study will not alter standard clinical care.

This is a single-center, prospective observational study designed to validate the performance of Glandy HYPER, a software medical device that analyzes sleep heart rate data from wearable devices in conjunction with thyroid function test (TFT) results to detect thyrotoxicosis. The study targets adults aged 22 or older with newly diagnosed or currently treated Graves' disease.

Each participant will wear a smartwatch (Apple or Samsung, depending on their smartphone OS) to measure heart rate during sleep over a 12-week period. Blood samples for TFTs will be collected at four separate visits (baseline and at 4, 8, and 12 weeks). The primary endpoint is the F1 score between the investigational device's output and the diagnosis of thyrotoxicosis based on free T4 values. Secondary endpoints include sensitivity, specificity, and area under the curve (AUC) of the device's performance.

Data from the wearable device and TFTs will be used to create multiple evaluation-reference data pairs per patient, enabling within-subject validation across different time points. The study does not involve any investigational treatment or alteration to standard care and is classified as non-significant risk (NSR). The output of the software device will not influence clinical decisions during the trial.

The study also aims to assess the generalizability of the software's performance by comparing results from this U.S.-based cohort with prior studies conducted in Korea.

Inclusion Criteria:

• Adults aged 22 years or older, regardless of sex.
• Individuals who are newly diagnosed with Graves' disease or currently undergoing treatment for it.
• Individuals who have received sufficient explanation about the investigational software and are able to use it appropriately.
• Individuals who voluntarily agree to participate in the study and have signed informed consent, either directly or via a legally authorized representative.

Exclusion Criteria:

• Individuals with cardiac conditions such as arrhythmia or heart failure.
• Individuals taking medications that significantly affect heart rate, including antiarrhythmics or antihistamines. (Intermittent short-acting beta-blockers are allowed.)
• Pregnant or breastfeeding individuals, or those planning pregnancy during the study period or not using appropriate contraception.
• Individuals with significant comorbidities that interfere with follow-up or study compliance.
• Individuals with severe psychiatric disorders, substance use disorder, or alcohol dependence.
• Individuals deemed ineligible at the discretion of the investigator for safety or ethical concerns.

Adults aged 22 years and older with a confirmed diagnosis of Graves' disease, including both newly diagnosed and currently treated individuals. Participants will be recruited from a single center in the United States. All participants must be able to use a wearable device and provide informed consent.

The individual participant data (IPD) collected in this study will not be shared with other researchers due to privacy concerns and the sensitive nature of the biometric and clinical data involved. Data are collected solely for regulatory and scientific validation purposes and will be handled in accordance with applicable privacy regulations.