Which lifestyle factors change TSH?

TSH (thyroid-stimulating hormone) is modulated by several lifestyle factors, though evidence comes mostly from observational and small interventional studies. Iodine intake is critical: both deficiency and excess alter TSH. Selenium (e.g., Brazil nuts, tuna) aids T4-to-T3 conversion; deficiency may raise TSH. Zinc deficiency is also linked to elevated TSH. Chronic stress impacts the HPA axis and can suppress or elevate TSH. Poor sleep and shift work disrupt circadian TSH rhythms. Moderate exercise tends to lower TSH slightly, while extreme endurance training may increase it. Smoking generally lowers TSH, while alcohol effects are inconsistent. Cruciferous vegetables (e.g., broccoli, kale) in very high raw amounts may interfere with thyroid function, but normal consumption is safe. Importantly, lifestyle changes usually cause modest TSH shifts; persistent abnormalities require medical evaluation. Evidence strength is moderate: few large RCTs exist. MyBody-X blood tests can measure TSH but cannot diagnose lifestyle causes; a physician’s assessment is essential.