Portal capillaries connect the hypothalamus and the adenohypophysis (also called the anterior pituitary or anterior lobe). This network of capillaries is called the hypophyseal portal system. The hypophyseal portal allows hypothalamic hormones to enter the anterior pituitary directly, avoiding the circulatory system altogether.
That process is important to the function of the endocrine system in your body, the system that uses hormones as signals for organ function throughout the body. This system is located in the front part of the brain, and it coordinates the nervous system, controls bodily needs like temperature and thirst, and is involved in your sleep.