[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Physiology](https://durgical.com/en/physiology/) › [Endocrine](https://durgical.com/en/physiology/#s-endocrine) › The hypothalamic–pituitary system: overview [Physiology](https://durgical.com/en/physiology/) · [Endocrine](https://durgical.com/en/physiology/#s-endocrine) # The hypothalamic–pituitary system: overview - Concept - Exam priority: high The hypothalamus gives orders to the pituitary, and the pituitary drives the thyroid, adrenals, gonads, liver and breast. Updated 2026-11-01 Also called: Hypophyseal portal system, Anterior and posterior pituitary **See it in 3D:** [Hypothalamus](https://durgical.com/en/anatomy/hypothalamus/) · [Pituitary gland](https://durgical.com/en/anatomy/pituitary-gland/) · [Sella turcica](https://durgical.com/en/anatomy/sella-turcica/) ## Key points - Anterior pituitary = true gland (oral ectoderm, Rathke's pouch); posterior pituitary = hypothalamic axons (neuroectoderm). - Prolactin is the only anterior pituitary hormone under tonic brake (dopamine): cut the stalk and prolactin RISES while the others fall. - The glycoprotein hormones (TSH, LH, FSH, hCG) share the α subunit; the β subunit gives specificity. - A macroadenoma pressing on the optic chiasm causes bitemporal hemianopia. - In progressive pituitary failure GH and gonadotropins go first; ACTH and TSH usually fail last. ## What it is The hypothalamus turns signals from the brain and the blood into releasing or inhibiting hormones. These travel through a short portal system to the anterior pituitary, which answers with six trophic hormones. The posterior pituitary is nerve tissue: it stores and releases ADH and oxytocin made in the hypothalamus. Almost every axis is braked by negative feedback from its final hormone. ## How it works, step by step - Neurons of the paraventricular, arcuate and other nuclei release hypothalamic hormones into the median eminence. - The primary capillary plexus picks them up and the long portal veins carry them, undiluted, to the anterior pituitary. - Each hypothalamic hormone acts on its own cell type: TRH on thyrotrophs, CRH on corticotrophs, GnRH on gonadotrophs, GHRH on somatotrophs. - The trophic hormone stimulates its target gland, which grows and secretes its final hormone. - The final hormone brakes hypothalamus and pituitary (long loop); the trophic hormone can also brake the hypothalamus (short loop). ### Hormone axes and feedback Hypothalamic–pituitary–thyroid axis **Lesion** None (normal) Tap a box to see the hormone, or choose a lesion to see the lab pattern. - Stimulates (+) - Inhibits / negative feedback (−) - Level ↑ - Level ↓ Illustrative schematic drawn by Durgical: simplified axes and classic lab patterns; not for clinical decisions. ### Hormone axes and feedback Hypothalamic–pituitary–adrenal axis **Lesion** None (normal) Tap a box to see the hormone, or choose a lesion to see the lab pattern. - Stimulates (+) - Inhibits / negative feedback (−) - Level ↑ - Level ↓ Illustrative schematic drawn by Durgical: simplified axes and classic lab patterns; not for clinical decisions. ## Anterior pituitary hormones | Hormone | Hypothalamic control | Target | Main action | | --- | --- | --- | --- | | [TSH](https://durgical.com/en/conditions/hypothyroidism/) | TRH (+) | Thyroid | T4/T3 synthesis and release; gland growth | | [ACTH](https://durgical.com/en/conditions/adrenal-insufficiency/) | CRH (+), ADH (+) | Adrenal cortex | Cortisol and adrenal androgens | | LH and FSH | Pulsatile GnRH (+) | Gonads | Sex steroids and gametogenesis | | [GH](https://durgical.com/en/conditions/pituitary-adenoma/) | GHRH (+), somatostatin (−) | Liver and tissues | IGF-1, growth, anti-insulin effect | | [Prolactin](https://durgical.com/en/conditions/pituitary-adenoma/) | Dopamine (−), TRH (+) | Breast | Milk production; suppresses GnRH | ## Clinical notes - Pituitary adenoma: it may oversecrete (prolactinoma, acromegaly, Cushing disease) or compress (headache, bitemporal hemianopia, hypopituitarism). - Stalk effect: a non-secreting mass that compresses the stalk raises prolactin a little by cutting off dopamine. - Sheehan syndrome: pituitary necrosis after postpartum hemorrhage; failure to lactate is often the first sign. ## Memory aid "Cut the stalk and everything drops except the milk": prolactin is the hormone that lives with the brake on. ## Test yourself Think of the answer, then tap the question to see it. ## Why does cutting the pituitary stalk raise prolactin while the other anterior pituitary hormones fall? Prolactin is under tonic inhibition by hypothalamic dopamine. Cutting the stalk removes dopamine (prolactin rises) and also removes TRH, CRH, GnRH and GHRH (the others fall). ## Which visual field defect does a macroadenoma with suprasellar extension cause, and why? Bitemporal hemianopia: the tumor presses on the chiasm from below and damages the crossing nasal fibers, which carry the temporal visual fields. ## Why do hypothalamic hormones work at such low concentrations on the anterior pituitary? They arrive through a direct portal system: from median-eminence capillaries straight to pituitary capillaries, without dilution in the whole blood volume. ## What do TSH, LH, FSH and hCG have in common, and what follows from it? They share the α subunit; the β subunit gives specificity. So very high hCG (molar pregnancy or first trimester) can stimulate the TSH receptor. [Add to my cards (4)](https://durgical.app/estudiar/?add=/en/physiology/the-hypothalamic-pituitary-system-overview/) ## See it in 3D The structures of Durgical's 3D anatomy where it happens. - [Hypothalamus](https://durgical.com/en/anatomy/hypothalamus/) - [Pituitary gland](https://durgical.com/en/anatomy/pituitary-gland/) - [Sella turcica](https://durgical.com/en/anatomy/sella-turcica/) ## Related topics - [The posterior pituitary: ADH and oxytocin](https://durgical.com/en/physiology/the-posterior-pituitary-adh-and-oxytocin/) - [The HPA axis and its circadian rhythm](https://durgical.com/en/physiology/the-hpa-axis-and-its-circadian-rhythm/) - [The thyroid axis: reading TSH and free T4](https://durgical.com/en/physiology/the-thyroid-axis-reading-tsh-and-free-t4/) - [Growth hormone and IGF-1](https://durgical.com/en/physiology/growth-hormone-and-igf-1/) - [Prolactin and its control by dopamine](https://durgical.com/en/physiology/prolactin-and-its-control-by-dopamine/) - [Hormones: types, receptors and feedback](https://durgical.com/en/physiology/hormones-types-receptors-and-feedback/) ## Related conditions - [Pituitary adenoma](https://durgical.com/en/conditions/pituitary-adenoma/) - [Hypothyroidism](https://durgical.com/en/conditions/hypothyroidism/) - [Adrenal insufficiency](https://durgical.com/en/conditions/adrenal-insufficiency/) ## In Biochemistry - [Hormone classes and mechanisms](https://durgical.com/en/biochemistry/topics/hormone-classes-and-mechanisms/) [← All of physiology](https://durgical.com/en/physiology/) Educational physiology content; not a diagnostic or treatment guide and no substitute for a health professional's advice. Values are approximate references. No doses are given. Sources: [17.3 The Pituitary Gland and Hypothalamus](https://openstax.org/books/anatomy-and-physiology-2e/pages/17-3-the-pituitary-gland-and-hypothalamus) (OpenStax (Rice University), 2022); [Anatomy, Head and Neck, Pituitary Gland](https://www.ncbi.nlm.nih.gov/books/NBK551529/) (StatPearls (NCBI Bookshelf), 2024); [Pituitary Adenoma](https://www.ncbi.nlm.nih.gov/books/NBK554451/) (StatPearls (NCBI Bookshelf), 2024); Hall JE. Guyton and Hall Textbook of Medical Physiology, 13th ed. (ch. 76). Reference book used to check facts; its text and figures are not reproduced (Elsevier, 2016). ## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake Representative model, for educational purposes only. --- Source: https://durgical.com/en/physiology/the-hypothalamic-pituitary-system-overview/ License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/physiology/the-hypothalamic-pituitary-system-overview/