Thyroid pill plus diet may boost weight loss in obesity, new trial suggests

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

Inclusion Criteria: * Adults 25-60 years of age. * Obesity grade I-II: BMI 30.0-39.9 kg/m². * Either subclinical hypothyroidism (TSH 5-10 mIU/L with normal peripheral hormones) or euthyroid with TSH in the highest tertile of the population reference range (no known thyroid disease). * Able and willing to provide written informed consent. * Women of childbearing potential: not pregnant or breastfeeding and using a highly effective contraception method (failure rate \<1%) per CTCG guidance (e.g., hormonal methods, IUD/IUS, sterilization, or dual barrier with spermicide). Exclusion Criteria: * Diabetes mellitus (HbA1c ≥6.5%, fasting glucose ≥126 mg/dL, or 2-h OGTT ≥200 mg/dL). * Any prior thyroid disease (hyperthyroidism, overt hypothyroidism) or prior LT4 treatment. * Current or recent (≤3 months) use of levothyroxine, hypoglycaemic agents, antibiotics, or regular probiotics/prebiotics. * Active cancer or cancer within the last 5 years (except basal-cell carcinoma). * Chronic liver disease with total bilirubin ≥2.0 mg/dL or AST \>3× ULN. * Established cardiovascular disease (e.g., stroke, ischemic heart disease, peripheral artery disease). * Atrial fibrillation or any arrhythmia history. * Uncontrolled hypertension (\>160/100 mmHg) despite therapy (assessed by ABPM at screening). * Any heart failure; resting HR \>85 bpm; eGFR \<60 mL/min. * Known HIV, HBV, or HCV infection. * Acute inflammatory disease or inflammatory bowel disease. * Serious underlying disease that, in the investigator's judgment, could affect participation. * Drug/alcohol abuse, life expectancy \<12 months, inability to follow the recommended diet or attend visits. * Positive pregnancy test, pregnant, expecting pregnancy, or breastfeeding. * Hypersensitivity to any component of the investigational product. * Inability or unwillingness to provide informed consent.