Hypothalamus
The body's thermostat and control center. The hypothalamus is a small brain region that links the nervous system to the endocrine system via the pituitary. It regulates body temperature, hunger, thirst, sleep, circadian rhythm, and stress response. It's the ultimate integrator of body signals.
Hypothalamic Functions
Temperature Regulation
Thermostat function. Triggers sweating, shivering. Fever response.
Hunger & Satiety
Integrates leptin, ghrelin signals. Controls appetite. Energy balance.
Circadian Rhythm
SCN (suprachiasmatic nucleus). Master clock. Light input via retina.
Stress Response
Releases CRH. Activates HPA axis. Cortisol cascade begins here.
Thirst
Osmoreceptors sense dehydration. Triggers thirst and ADH release.
Sleep-Wake Cycle
Orexin/hypocretin system. Wakefulness promotion. Narcolepsy connection.
Hypothalamic Hormones
TRH
Thyrotropin-releasing hormone. Signals pituitary to release TSH. Thyroid axis.
CRH
Corticotropin-releasing hormone. Triggers ACTH. Stress/cortisol axis.
GnRH
Gonadotropin-releasing hormone. Controls LH/FSH. Reproductive axis.
GHRH
Growth hormone-releasing hormone. Stimulates growth hormone release.
Dopamine
Inhibits prolactin release. Hypothalamic dopamine different from reward dopamine.
Somatostatin
Inhibits growth hormone and TSH. Brake signal. Balance function.
Hypothalamic Dysfunction
HPA Axis Dysregulation
Chronic stress alters setpoint. Cortisol patterns disrupted. Burnout.
Leptin Resistance
Hypothalamus stops responding to leptin. Hunger persists. Obesity cycle.
Circadian Disruption
Shift work, jet lag, light at night. Downstream effects on all hormones.
Hypothalamic Amenorrhea
GnRH suppression from stress, low calories, excessive exercise. Period stops.