Which hormone is primarily responsible for regulating metabolism?

Thyroid hormone, particularly thyroxine (T4), plays a crucial role in regulating metabolism by influencing the rate at which your body converts food into energy. It affects almost every cell in the body, stimulating metabolism and thereby impacting growth and development, as well as the metabolic activities of various organs. Elevated levels of thyroid hormone increase the basal metabolic rate, which is the rate of energy expenditure at rest, promoting the utilization of carbohydrates, fats, and proteins.

In contrast, while insulin is vital for glucose metabolism and managing blood sugar levels, and cortisol has a role in stress response and metabolism, they don't primarily regulate metabolic processes to the same extent as thyroid hormones do. Adrenaline, on the other hand, is primarily involved in the fight-or-flight response and can influence metabolism in terms of energy utilization during stress but does not serve as the central regulator of metabolism over an extended period.