Hypothalamus co-ordinates seasonal and circadian rhythms, complex patterns of neuroendocrine outputs, complex homeostatic mechanisms and many important stereotyped behaviours.
Hypothalamus responds to many different signals, some of which are generated externally and some internally.
It is connected with many parts of the CNS, including the brainstem reticular formation and autonomic zones, the limbic forebrain (particularly the amygdala, septum, diagonal band of Broca, and the olfactory bulbs, and the cerebral cortex).
Hypothalamus responses to light, olfactory stimuli, steroids, including gonadal steroids and corticosteroids, generates circadian and seasonal rhythms; neutrally transmits internal/visceral information, arising in particular from the heart, the stomach, and the reproductive tract.
Hypothalamus reacts on blood-borne stimuli, including Leptin, Ghrelin, angiotensin, insulin, pituitary hormones, cytokines, plasma concentrations of glucose and osmolarity etc. Cholecystokinin is conveying the feeling of satiety to the brain; Leptin is increasing feeling of satiety, Ghrelin increases when the stomach is empty.