The primary hormone involved in regulating metabolism is thyroxine (T4), produced by the thyroid gland. Thyroxine influences how quickly the body uses energy, regulates proteins, and controls the sensitivity to other hormones. In conjunction with its active form, triiodothyronine (T3), it plays a significant role in metabolic processes, including the conversion of carbohydrates and fats into energy. Proper thyroid function is critical for maintaining metabolic health and overall well-being.