What role does TSH play in weight loss?

TSH (thyroid-stimulating hormone) controls thyroid hormone release, which directly influences basal metabolic rate. Elevated TSH typically indicates hypothyroidism (underactive thyroid), linked to a slower metabolism and weight gain. Low TSH suggests hyperthyroidism (overactive thyroid), which accelerates metabolism and often causes weight loss. However, TSH itself does not directly cause weight loss; it is a diagnostic marker. Even in subclinical thyroid dysfunction, the impact on weight is modest and interacts with diet, exercise, and genetics. Using TSH as a weight-loss lever without medical supervision is unsafe—self-medicating with thyroid hormones can lead to serious side effects like arrhythmias. Evidence: human-strong (well-established physiology).