In the anatomy of mammals, the hypothalamus is a region of the brain located below the thalamus, forming the major portion of the ventral region of the diencephalon and functioning to regulate certain metabolic processes and other autonomic activities. The hypothalamus links the nervous system to the endocrine system by synthesizing and secreting neurohormones often called releasing hormones because they function by stimulating the secretion of hormones from the anterior pituitary gland — among them, gonadotropin-releasing hormone (GnRH). The neurons that secrete GnRH are linked to the limbic system, which is very involved in the control of emotions and sexual activity. The hypothalamus is also the area of the brain that controls body temperature, hunger and thirst, and circadian cycles.

The hypothalamus connects to the pituitary gland via the tuberoinfundibular pathway.

Hypothalamic nuclei

Region	Medial Area	Lateral Area
Anterior	Medial preoptic nucleus Supraoptic nucleus Paraventricular nucleus Anterior nucleus Suprachiasmatic nucleus	Lateral preoptic nucleus Lateral nucleus Part of supraoptic nucleus
Tuberal	Dorsomedial nucleus Ventromedial nucleus Arcuate nucleus	Lateral nucleus Lateral tuberal nuclei
Posterior	Mammillary nuclei (part of mammillary bodies) Posterior nucleus	Lateral nucleus

See also: limbic system, HPA axis, cluster headaches