Hypothalamus

The hypothalamus links the nervous system to the endocrine system via the pituitary gland (hypophysis). The hypothalamus, (from Greek ὑποθαλαμος = under the thalamus) is located below the thalamus, just above the brain stem. This gland occupies the major portion of the ventral region of the diencephalon. It is found in all mammalian brains, including humans. It is roughly the size of an almond.

The hypothalamus gland regulates certain metabolic processes and other autonomic activities. It synthesizes and secretes neurohormones, often called releasing hormones, as needed that control the secretion of hormones from the anterior pituitary gland.

The hypothalamus controls body temperature, hunger, thirst, and circadian cycles. Also, among other hormones, it releases gonadotropin releasing hormone (GnRH). The neurons that secrete GnRH are linked to the limbic system, which is primarily involved in the control of emotions and sexual activity.