Which hormone primarily regulates the body’s metabolic processes?

Thyroxine, also known as T4, is the primary hormone that regulates the body's metabolic processes. It is produced by the thyroid gland and plays a pivotal role in controlling the rate of metabolism, which includes how the body converts food into energy. Thyroxine influences various physiological functions such as heart rate, temperature regulation, and the metabolism of carbohydrates, proteins, and fats.

When released into the bloodstream, thyroxine increases the basal metabolic rate, promoting the catabolism of fats and proteins, and enhancing carbohydrate metabolism. It is crucial for normal growth and development, especially in infants and children, where adequate levels support proper brain development and overall physical growth.

Other hormones listed may influence metabolic activities, but they do not primarily regulate metabolism to the extent that thyroxine does. For instance, epinephrine primarily affects the body's acute stress response, growth hormone impacts growth and muscle mass, and prolactin mainly regulates lactation and has roles in reproductive health. Thus, thyroxine stands out as the key hormone in metabolic regulation.