Which hormone is primarily responsible for regulating metabolism in the body?

Thyroxine, which is produced by the thyroid gland, plays a critical role in regulating metabolism in the body. This hormone is essential for the growth and development of tissues, as well as for the overall metabolic rate, which includes how quickly the body uses energy and processes nutrients. Thyroxine increases the metabolic rate of cells, influencing energy production and consumption. It directly affects processes such as protein synthesis and glucose metabolism, thereby impacting overall energy balance and metabolic functions.

In contrast, while insulin is important for glucose metabolism and helps regulate blood sugar levels, its primary role is not in the overall regulation of metabolism but rather in controlling the use of sugar and fat. Cortisol, often referred to as the stress hormone, does regulate certain aspects of metabolism, particularly during stress responses, but it is not the primary hormone responsible for basal metabolic rate. Estrogen primarily influences reproductive functions and affects some metabolic processes but does not have the same overarching role in metabolic regulation as thyroxine does.