Thyroid hormone is primarily responsible for regulating metabolism in the body. It influences how the body converts food into energy, affecting overall metabolic rate and energy expenditure. An optimal balance of thyroid hormones is crucial, as both hyperthyroidism (overactive) and hypothyroidism (underactive) can lead to significant health issues, including weight fluctuations, fatigue, and hormonal imbalances. Maintaining healthy thyroid function is essential for managing weight, energy levels, and overall well-being.