In the human brain the hypothalamus is an area the size of an almond located above the pituitary gland, and acts as a master-regulator in the endocrine system. The hypothalamus acts as a link between the nervous and endocrine systems by being connected neurally to the brainstem, amygdala and septum, and synthesising hormones together with the pituitary gland to regulate many body processes (homeostasis, hunger, circadian rhythm, reproduction, defence, etc.).
Therefore, the signals given by different systems including the heart, stomach and reproductive tract, as well as other forms of stimuli e.g. blood-borne molecules, stress, steroids, olfaction, are processed via the hypothalamus and contribute to the way many hormones are secreted. The hypothalamus is split into multiple regions called nuclei that govern different functions.
Some of these hormones (secreted by the anterior pituitary specifically) include dopamine, growth-hormone-releasing hormone and gonadotropin-releasing hormone. These are involved in reward behaviour, growth and reproduction respectively.
The posterior pituitary releases oxytocin and vasopressin with roles in reproduction and kidney function.