Which endocrine gland is primarily responsible for regulating metabolism?

The thyroid gland is primarily responsible for regulating metabolism because it produces hormones such as thyroxine (T4) and triiodothyronine (T3), which play critical roles in controlling the speed at which the body uses energy, processes food, and maintains overall metabolic balance. These hormones influence various physiological processes, including heart rate, body temperature, and the rate of energy expenditure.

For example, higher levels of thyroid hormones lead to an increased metabolic rate, which can result in weight loss and increased energy, while lower levels can slow down metabolism, leading to weight gain and fatigue. Thus, the thyroid gland's regulation of these hormones is vital for maintaining metabolic health and homeostasis in the body.