The hypothalamus is the link between the endocrine and nervous systems via the pituitary gland. It receives information from the nervous system and uses it for the production of hormones. These hormones signal the pituitary gland to start and stop the production of other hormones. Broadly speaking, the hypothalamus is involved in autonomic (involuntary), endocrine, and behavioral functions. Some functions include thirst and hunger, mood, sleep, metabolism, and growth. Its primary function, however, is homeostasis.
Homeostasis is the ability for an organism to maintain internal stability. It involves the balance of electrolytes, fluids, body temperature, weight, blood pressure and sugar, and acidity. Your body’s stability is largely due to the hypothalamus’ production and regulation of hormones in your body. To do this, the hypothalamus maintains a set-point it uses to regulate the body. For instance, the set-point for internal temperature would be 98.6°F. If you are in an environment that is colder than that, it regulates your body’s processes via hormones to ultimately convert energy into heat. If the environment is warmer, signals will be sent to start sweat production to cool off the body.