Which hormone primarily regulates metabolism?

Thyroid hormones, primarily thyroxine (T4) and triiodothyronine (T3), are the main regulators of metabolism in the body. These hormones are produced by the thyroid gland and play a crucial role in controlling the rate of metabolic processes, including how the body utilizes energy. They influence the metabolic rate of nearly every cell in the body, affecting the conversion of nutrients into energy and the overall energy expenditure.

By promoting the metabolism of carbohydrates, fats, and proteins, thyroid hormones ensure that energy production is aligned with the body’s needs, which is essential for maintaining homeostasis, growth, and development. When there is an imbalance in thyroid hormone levels—such as in hyperthyroidism or hypothyroidism—metabolism can be significantly altered, leading to various health issues.

Insulin, cortisol, and adrenaline also contribute to metabolic processes but in more specific contexts. Insulin primarily regulates glucose metabolism and promotes the storage of energy, while cortisol is more involved in the stress response and modulating metabolism during times of stress. Adrenaline serves to increase energy availability during 'fight or flight' situations but does not have the broad regulatory role that thyroid hormones do in day-to-day metabolic function.