The brain region that regulates body temperature and metabolism is the hypothalamus.
This small structure lies below the thalamus in the diencephalon, near the base of the brain and around the third ventricle. Its name literally means “below the thalamus.” Although only about almond-sized in humans, it contains specialized nuclei that coordinate many automatic body functions.
For temperature control, the hypothalamus acts like a biological thermostat. It can trigger sweating and widening of skin blood vessels when the body is hot, or shivering and heat conservation when it is cold. It also helps regulate hunger, thirst, sleep, circadian rhythms and energy balance.
The hypothalamus is often confused with the pituitary gland. The pituitary releases many hormones, but the hypothalamus directs it through releasing hormones and neural signals. The thalamus, by contrast, is chiefly involved in relaying sensory and motor information rather than serving as the body’s main temperature-control center.