Hypothalamus & Pituitary

Anatomy

• Floor and lower lateral walls of the third ventricle; below the thalamus (hypothalamic sulcus). The lamina terminalis and optic chiasm lie in front, the mammillary bodies behind.
• Nuclei: suprachiasmatic (SCN — circadian clock), paraventricular (CRH, oxytocin, vasopressin), supraoptic (ADH), arcuate (appetite, GnRH network, dopamine), ventromedial (satiety, defense), lateral (orexin/hypocretin), preoptic (temperature, sleep — VLPO).
• Pituitary: anterior lobe (hormonal control via portal vessels), posterior lobe (axonal release of oxytocin and ADH).
• Blood supply: branches of the circle of Willis, superior hypophyseal artery.

Functions

• Homeostasis: body temperature, hunger–satiety, thirst and water balance.
• Sleep–wake and circadian rhythm (SCN, orexin, VLPO).
• Neuroendocrine axes: HPA (stress–cortisol), HPG (puberty), HPT (thyroid), growth hormone, prolactin.
• Top-level control of the autonomic nervous system.
• Basic motivated behaviors: feeding, sex, defense; attachment and social bonding (oxytocin, vasopressin).

Connections and chemistry

• Pituitary (portal system, neurohypophysis)
• Amygdala and BNST (stria terminalis)
• Hippocampus (fornix)
• Brainstem autonomic nuclei and PAG
• Retina → SCN (retinohypothalamic tract)
• Orexin, histamine (tuberomammillary), oxytocin, CRH

Development

Developmental course through childhood and adolescence.

• Onset of puberty: reactivation of pulsatile GnRH release (kisspeptin).
• Circadian phase delay in adolescence: melatonin is released later, a tendency to go to bed late.
• Early-life stress changes the programming of the HPA axis.

Clinical

• Anorexia nervosa: hypothalamic amenorrhea (HPG suppression), HPA activation.
• Antipsychotic-related weight gain (H1, 5-HT2C) and hyperprolactinemia (tuberoinfundibular D2 blockade).
• Narcolepsy type 1: 85–95% of the orexin (hypocretin) neurons in the lateral hypothalamus are lost; neighboring MCH neurons are spared, and gliosis suggests a degenerative (probably autoimmune) process (Thannickal et al., 2000). Onset is often in childhood and adolescence; it can be mistaken for an attention problem or depression. B
• Prader-Willi syndrome (hyperphagia), craniopharyngioma (hypothalamic obesity, behavior change).
• Hypothalamic hamartoma: gelastic (laughing) seizures, precocious puberty, behavior problems.
• Early puberty in girls is associated with increased risk of depression and anxiety.
• Oxytocin in autism: in 290 children aged 3–17, 24 weeks of intranasal oxytocin did not improve social function more than placebo (SOARS-B; Sikich et al., 2021). Off-label use is not supported. B

Treatment

This region from the perspective of medication, psychotherapy and neuromodulation. Letter badges are evidence levels.

• Narcolepsy (children): sodium oxybate is FDA-approved from age 7 for cataplexy and daytime sleepiness (2018); pitolisant (an H3 receptor inverse agonist that increases histamine release) is FDA-approved from age 6 for daytime sleepiness (2024). Both compensate downstream of orexin loss. A
• Prader-Willi syndrome: diazoxide choline (extended release) is the first FDA-approved drug for hyperphagia, from age 4 (March 2025). A
• Monogenic and syndromic obesity: setmelanotide (MC4R agonist) is FDA-approved from age 2 for POMC, PCSK1 or LEPR deficiency and Bardet-Biedl syndrome, and from age 4 for acquired hypothalamic obesity (e.g. after craniopharyngioma). Direct targeting of the hypothalamic satiety pathway. A
• Central precocious puberty: GnRH agonists halt pubertal progression by desensitizing the pituitary. B
• Antipsychotic monitoring: weight, fasting glucose, lipids and prolactin; hyperprolactinemia comes from tuberoinfundibular D2 blockade.
• Oxytocin: ineffective for social function in autism (Sikich et al., 2021). B

Assessment

Neuropsychological tasks and measures that probe this region's function.

• Endocrine assessment: cortisol rhythm, prolactin (antipsychotic monitoring), thyroid
• Actigraphy and sleep diary
• Growth chart, Tanner pubertal staging

Lesions and damage

Clinical findings expected with damage or dysfunction.

• Diabetes insipidus, hypo/hyperthermia.
• Hyperphagia and obesity or cachexia; sleep disorders.
• Rage attacks (ventromedial), endocrine deficiencies, memory impairment (mammillary bodies).

In the model

How this structure is defined in the 3D model, and the data source.

CIT168 hypothalamus and mammillary body probability map (threshold 0.35). The pituitary and its stalk are approximate shapes positioned from the T1 image.

References

Full citations for the card; links go to the paper (DOI) or a PubMed search.

1. Thannickal TC et al. Reduced number of hypocretin neurons in human narcolepsy. Neuron 2000;27:469–474. Search PubMed
2. Sikich L et al. Intranasal oxytocin in children and adolescents with autism spectrum disorder. N Engl J Med 2021. Search PubMed
3. FDA kararları: Xyrem (sodyum oksibat) pediatrik, Ekim 2018; Wakix (pitolisant) 6 yaş and üstü, Haziran 2024; Vykat XR (diazoksit kolin), Mart 2025; Imcivree (setmelanotid) 2 yaş and üstü and hipotalamik obezite. Search PubMed