# 07 Pituitary Secretions ## Hypothalamus-Pituitary System [\_](https://github.com/thisispiggy/my-wiki/tree/601ff771dc2fac1318ae8b59435ac8485628fd81/01%20Step%201/Endocrinology/How%20does%20anterior%20pituitary%20communicate%20with%20hypothalamus?/README.md)The anterior lobe of the pituitary gland communicates with the hypothalamus by the *hypothalamic–hypophysial portal system:* 1. The hypothalamus is supplied by blood coming from the **superior hypophyseal artery.** 2. Hypothalamic hormones enter the **capillary plexus** near the median eminence, and travel via **long portal veins** to the anterior pituitary. 3. In the anterior pituitary, hormones exit a **secondary capillary plexus** to stimulate or inhibit hormone release from their specific endocrine target cells. 4. Endocrine cells respond by increasing or decreasing their output of tropic hormones into systemic circulation. ![](https://f001.backblazeb2.com/file/wikiFiles/87SYYdG.jpg) ![](https://f001.backblazeb2.com/file/wikiFiles/X8SAlDA.jpg) Hypothalamus outlined on MRI: ![](https://f001.backblazeb2.com/file/wikiFiles/jr6CpX1.jpg) .. [\_](https://github.com/thisispiggy/my-wiki/tree/601ff771dc2fac1318ae8b59435ac8485628fd81/01%20Step%201/Endocrinology/How%20does%20posterior%20pituitary%20communicate%20with%20hypothalamus?/README.md)In contrast, the posterior lobe of the pituitary gland contains the axons of neurons whose cell bodies are located in hypothalamic nuclei. 1. Hormones are synthesized in the hypothalamus, packaged in secretory granules and transported down the nerve axons for secretion. 2. Upon stimulation of the hypothalamic cell bodies, hormone-containing granules are released by exocytosis into peripheral circulation, via the **capillary plexus of the inferior hypophyseal artery.** ![](https://f001.backblazeb2.com/file/wikiFiles/87SYYdG.jpg).. [\_](https://github.com/thisispiggy/my-wiki/tree/601ff771dc2fac1318ae8b59435ac8485628fd81/01%20Step%201/Endocrinology/Hypothalamus%20secretes%20these%20hormones/README.md) ![](https://f001.backblazeb2.com/file/wikiFiles/pQOk9fT.jpg) .. ### CRH [\_](https://github.com/thisispiggy/my-wiki/tree/601ff771dc2fac1318ae8b59435ac8485628fd81/01%20Step%201/Endocrinology/Corticotropin%20releasing%20hormone%20function/README.md)Stimulates **ACTH secretion**, as well as the release of other peptides derived from proopiomelanocortin (e.g. **MSH, β-endorphin**)., ![](https://f001.backblazeb2.com/file/wikiFiles/pQOk9fT.jpg) ### GnRH [\_](https://github.com/thisispiggy/my-wiki/tree/601ff771dc2fac1318ae8b59435ac8485628fd81/01%20Step%201/Endocrinology/Gonadotropin%20releasing%20hormone%20function/README.md)Stimulates the secretion of **LH**, **FSH**., ![](https://f001.backblazeb2.com/file/wikiFiles/pQOk9fT.jpg) ### Somatostatin [\_](https://github.com/thisispiggy/my-wiki/tree/601ff771dc2fac1318ae8b59435ac8485628fd81/01%20Step%201/Endocrinology/Somatostatin%20function/README.md)Inhibits the secretion of **GH** and **TSH**., ![](https://f001.backblazeb2.com/file/wikiFiles/pQOk9fT.jpg) [\_](https://github.com/thisispiggy/my-wiki/tree/601ff771dc2fac1318ae8b59435ac8485628fd81/01%20Step%201/Endocrinology/Synthetic%20somatostatin,%20octreotide,%20uses/README.md)Pharm uses: ![](https://f001.backblazeb2.com/file/wikiFiles/7g2n77t.jpg).. ### TRH [\_](https://github.com/thisispiggy/my-wiki/tree/601ff771dc2fac1318ae8b59435ac8485628fd81/01%20Step%201/Endocrinology/Thyrotropin%20releasing%20hormone,%20TRH,%20function.%20How%20does%20it%20affect%20dopamine)Stimulates the secretion of TSH and prolactin. Prolactin is under tonal dopamine inhibition, and **excess TRH levels suppress dopamine**. Thus, prolactin levels will increase as dopamine decreases., ![](https://f001.backblazeb2.com/file/wikiFiles/pQOk9fT.jpg) ### Dopamine [\_](https://github.com/thisispiggy/my-wiki/tree/601ff771dc2fac1318ae8b59435ac8485628fd81/01%20Step%201/Endocrinology/Dopamine,%20also%20known%20as%20prolactin%20release-inhibiting%20hormone,%20function/README.md)Inhibits the release of **prolactin**., ![](https://f001.backblazeb2.com/file/wikiFiles/pQOk9fT.jpg) ### Melanocyte Inhibiting Factor [\_](https://github.com/thisispiggy/my-wiki/tree/601ff771dc2fac1318ae8b59435ac8485628fd81/01%20Step%201/Endocrinology/Melanocyte%20inhibiting%20factor%20function/README.md)**Inhibits the release of MSH**., ![](https://f001.backblazeb2.com/file/wikiFiles/pQOk9fT.jpg) ## Anterior Pituitary [\_](https://github.com/thisispiggy/my-wiki/tree/601ff771dc2fac1318ae8b59435ac8485628fd81/01%20Step%201/Endocrinology/Anterior%20pituitary%20secretes%20these%20hormones/README.md)There are 6 major hormones secreted by the anterior pituitary (mnemonic: **FLAT P**i**G**): * **F**ollicle stimulating hormone (FSH) * **L**uteinizing hormone (LH) * **A**drenocorticotropic hormone (ACTH) * **T**hyroid stimulating hormone (TSH; thyrotropin) * **P**rolactin * **G**rowth hormone (GH) ![](https://f001.backblazeb2.com/file/wikiFiles/dt3I1Bs.jpg) .. ### FSH and LH [\_](https://github.com/thisispiggy/my-wiki/tree/601ff771dc2fac1318ae8b59435ac8485628fd81/01%20Step%201/Endocrinology/FSH,%20LH%20secreted%20by/README.md)Secreted by gonadotropes of the anterior pituitary., ![](https://f001.backblazeb2.com/file/wikiFiles/dt3I1Bs.jpg) [\_](https://github.com/thisispiggy/my-wiki/tree/601ff771dc2fac1318ae8b59435ac8485628fd81/01%20Step%201/Endocrinology/FSH/LH%20function/README.md) | | LH | FSH | | ---------- | ---------------------------------------------------------- | ----------------------------------- | | **Male** | **Leydig cell:** | **Sertoli Cell:** | | | testosterone synthesis | sperm maturation | | **Female** | **Theca Cell:** | **Granulosa Cell:** | | | testosterone synthesis, ovulation, corpus luteum formation | follicle growth, estrogen secretion | .. ### ACTH [\_](https://github.com/thisispiggy/my-wiki/tree/601ff771dc2fac1318ae8b59435ac8485628fd81/01%20Step%201/Endocrinology/ACTH%20secreted%20by%20and%20function/README.md)Secreted by corticotrophs of the anterior pituitary and stimulates adrenal growth and steroidogenesis., ![](https://f001.backblazeb2.com/file/wikiFiles/dt3I1Bs.jpg) ### TSH [\_](https://github.com/thisispiggy/my-wiki/tree/601ff771dc2fac1318ae8b59435ac8485628fd81/01%20Step%201/Endocrinology/TSH%20is%20secreted%20by%20and%20function/README.md)Secreted by thyrotrophs of the anterior pituitary and stimulates **thyroid hormone synthesis** and **release**., ![](https://f001.backblazeb2.com/file/wikiFiles/dt3I1Bs.jpg) ### GH [\_](https://github.com/thisispiggy/my-wiki/tree/601ff771dc2fac1318ae8b59435ac8485628fd81/01%20Step%201/Endocrinology/Growth%20hormone%20secreted%20by%20and%20function/README.md)Secreted by somatotropes of the anterior pituitary and is counter-regulatory to insulin. It stimulates **linear height growth** via **insulin-like growth factor** (IGF-1), which is released by the liver in response to stimulation by GH., ![](https://f001.backblazeb2.com/file/wikiFiles/dt3I1Bs.jpg) [\_](https://github.com/thisispiggy/my-wiki/tree/601ff771dc2fac1318ae8b59435ac8485628fd81/01%20Step%201/Endocrinology/GH%20secretion%20increased%20by%20and%20how/README.md)Growth hormone-releasing hormone (**GHRH**, somatocrinin) stimulates the secretion in **pulsatile fashion**. Also increased by * **Exercise** * **Sleep** (very high just after onset of sleep) * **Starvation (hypoglycemia)** ., [\_](https://github.com/thisispiggy/my-wiki/tree/601ff771dc2fac1318ae8b59435ac8485628fd81/01%20Step%201/Endocrinology/GH%20decreased%20by/README.md)Is decreased by: * Glucose * Somatostatin (released in response to IGF-1; GH) * IGF-1 (direct and indirect)., ![](https://f001.backblazeb2.com/file/wikiFiles/BCB3uKd.jpg) [\_](https://github.com/thisispiggy/my-wiki/tree/601ff771dc2fac1318ae8b59435ac8485628fd81/01%20Step%201/Endocrinology/GH%20and%20prolactin%20type%20of%20hormone/README.md)**Protein hormone** and binds to surface receptors, uses JAK2-STAT pathway., #### Growth Hormone Receptor [\_](https://github.com/thisispiggy/my-wiki/tree/601ff771dc2fac1318ae8b59435ac8485628fd81/01%20Step%201/Endocrinology/Growth%20hormone%20and%20prolactin%20receptor%20type%20and%20MOA/README.md) ![](https://f001.backblazeb2.com/file/wikiFiles/ZXl5Pds.jpg) ![](https://f001.backblazeb2.com/file/wikiFiles/yviEfp5.jpg).. #### IGF-1 [\_](https://github.com/thisispiggy/my-wiki/tree/601ff771dc2fac1318ae8b59435ac8485628fd81/01%20Step%201/Endocrinology/IGF-1%20aka/README.md)aka **Somatomedin**., [\_](https://github.com/thisispiggy/my-wiki/tree/601ff771dc2fac1318ae8b59435ac8485628fd81/01%20Step%201/Endocrinology/IGF-1%20secreted%20where/README.md)Many growth hormone receptors are found in the **liver**, and they secrete IGF-1, which mediates many of GH effects. IGF-1 is also produced in **peripheral tissues** and mediates its effect in paracrine fashion... [\_](https://github.com/thisispiggy/my-wiki/tree/601ff771dc2fac1318ae8b59435ac8485628fd81/01%20Step%201/Endocrinology/IGF%20effects/README.md)Has following effects: * Stimulates chondrocytes, increase **linear growth** * Stimulates muscles, **increase lean muscle mass** * Stimulates organs, **increase organ size** ., [\_](https://github.com/thisispiggy/my-wiki/tree/601ff771dc2fac1318ae8b59435ac8485628fd81/01%20Step%201/Endocrinology/IGF-1%20lab%20important%20because/README.md)IGF-1 is measured in serum as **indicator of GH function**, as GH is difficult to measure with its pulsatile fashion... #### GH Effects [\_](https://github.com/thisispiggy/my-wiki/tree/601ff771dc2fac1318ae8b59435ac8485628fd81/01%20Step%201/Endocrinology/GH%20effects/README.md)Has following effects: * Increased insulin resistance and blood sugar * Increased lipolysis by activating hormone sensitive lipase * Increased IGF-1 that results in bone, muscle, and organ growths., ![](https://f001.backblazeb2.com/file/wikiFiles/BCB3uKd.jpg) [\_](https://github.com/thisispiggy/my-wiki/tree/601ff771dc2fac1318ae8b59435ac8485628fd81/01%20Step%201/Endocrinology/GH%20blood%20glucose%20effects/README.md)GH **decreases blood glucose intake in to cells** and will cause anti-insulin effects: * increased blood sugar (diabetogenic) * increased insulin resistance in peripheral tissues * hyperinsulinemia., ![](https://f001.backblazeb2.com/file/wikiFiles/MEGw2i0.jpg) #### GH Deficiency [\_](https://github.com/thisispiggy/my-wiki/tree/601ff771dc2fac1318ae8b59435ac8485628fd81/01%20Step%201/Endocrinology/GH%20deficiency%20cause/README.md)Most common caues is pituitary tumor from masses or as result of surgery/radiation... [\_](https://github.com/thisispiggy/my-wiki/tree/601ff771dc2fac1318ae8b59435ac8485628fd81/01%20Step%201/Endocrinology/GH%20deficiency%20symptoms/README.md)Symptoms are different for children and adults: * Children: failure to grow * Adults: increased fat, low lean body mass, low energy.. [\_](https://github.com/thisispiggy/my-wiki/tree/601ff771dc2fac1318ae8b59435ac8485628fd81/01%20Step%201/Endocrinology/GH%20deficiency%20treatment/README.md)Treatment is synthetic growth hormone and IGF-1 level monitoring.. ### HCG [\_](https://github.com/thisispiggy/my-wiki/tree/601ff771dc2fac1318ae8b59435ac8485628fd81/01%20Step%201/Endocrinology/HCG%20and%20TSH,%20LH,%20FSH%20similarities/README.md)TSH, LH, FSH and human chorionic gonadotropin (hCG) share a common α-subunit, while the **β-subunit of these hormones determines hormone specificity**. ![](https://f001.backblazeb2.com/file/wikiFiles/dt3I1Bs.jpg).. ### MSH [\_](https://github.com/thisispiggy/my-wiki/tree/601ff771dc2fac1318ae8b59435ac8485628fd81/01%20Step%201/Endocrinology/MSH%20aka/README.md)aka melanotropin., [\_](https://github.com/thisispiggy/my-wiki/tree/601ff771dc2fac1318ae8b59435ac8485628fd81/01%20Step%201/Endocrinology/MSH%20secreted%20by%20and%20function/README.md)MSH, or melanotropin, stimulates melanin synthesis and is secreted from the **intermediate lobe** of the pituitary... \[\_]\(MSH and Cushing's disease)In Cushing's disease, the ACTH adenoma produces both excess ACTH and MSH, causing the characteristic darkened skin... ### POMC [\_](https://github.com/thisispiggy/my-wiki/tree/601ff771dc2fac1318ae8b59435ac8485628fd81/01%20Step%201/Endocrinology/MSH%20and%20ACTH%20similarities/README.md)Derived from **pro-opiomelanocortin (POMC)**., ![](https://f001.backblazeb2.com/file/wikiFiles/zHVkzVE.jpg) ### Basophils and Acidophils [\_](https://github.com/thisispiggy/my-wiki/tree/601ff771dc2fac1318ae8b59435ac8485628fd81/01%20Step%201/Endocrinology/Acidophils%20and%20basophils%20of%20anterior%20pituitary/README.md)Cells of the anterior pituitary are categorized into two groups, basophils and acidophils, based on whether they stain readily with acidic or basic dyes. To remember which type of hormone-secreting cells fall into which category, use the mnemonics “**GPA**” and “**B FLAT**”: * “**GPA**”: **G**rowth hormone and **P**rolactin are secreted by **A**cidophils * “**B FLAT**”: **B**asophils secrete **F**ollicle stimulating hormone, **L**utenizing hormone, **A**drenocorticotropic hormone, and **T**hyroid stimulating hormone... ![](https://f001.backblazeb2.com/file/wikiFiles/EPPvHZ4.jpg) ### Feedback [\_](https://github.com/thisispiggy/my-wiki/tree/601ff771dc2fac1318ae8b59435ac8485628fd81/01%20Step%201/Endocrinology/Feedback%20in%20hypothalamus/README.md)Anterior pituitary hormones enter the systemic circulation and exert their effects at target glands. Eventually, the target gland response is limited by its hormonal product exerting **negative feedback inhibition** at the level of the pituitary gland or hypothalamus... ## Posterior Pituitary [\_](https://github.com/thisispiggy/my-wiki/tree/601ff771dc2fac1318ae8b59435ac8485628fd81/01%20Step%201/Endocrinology/Posterior%20pituitary%202%20nuclei%20and%20their%20products/README.md): * Paraventricular nuclei: Oxytocin * Supraoptic nuclei: ADH.. [\_](https://github.com/thisispiggy/my-wiki/tree/601ff771dc2fac1318ae8b59435ac8485628fd81/01%20Step%201/Endocrinology/Posterior%20pituitary%20secretes,%20how/README.md)**Vasopressin** and **oxytocin** are two hormones that are secreted from the posterior pituitary. Note that vasopressin is also called antidiuretic hormone (ADH) and arginine vasopressin (AVP). The hypothalamus directly synthesizes hormones, which are complexed with neurophysins and shipped into the posterior pituitary for storage and secretion. The hypothalamic-pituitary hormones that utilize this *non-capillary* secretion mechanism include **arginine vasopressin** (aka antidiuretic hormone) and **oxytocin**... ![](https://f001.backblazeb2.com/file/wikiFiles/3GC5ofS.jpg) ### ADH [\_](https://github.com/thisispiggy/my-wiki/tree/601ff771dc2fac1318ae8b59435ac8485628fd81/01%20Step%201/Endocrinology/ADH%20is,%20made%20in/README.md)A nonapeptide that is synthesized predominately in the **supraoptic nucleus** of the hypothalamus, and secreted from the **posterior pituitary** upon stimulation of these cell bodies. ., [\_](https://github.com/thisispiggy/my-wiki/tree/601ff771dc2fac1318ae8b59435ac8485628fd81/01%20Step%201/Endocrinology/ADH%20and%20Oxytocin%20transported%20how%20and%20carrier%20protein/README.md)Travels down the nerve axon in neurosecretory granules to be stored in the nerve terminals, lying in the posterior pituitary gland. **Neurophysins** are the carrier proteins which make this transport possible., \[\_]\(ADH's 2 main effects)Vasopressin has an **antidiuretic effect** (reabsorbs water) and is also a moderate **vasoconstrictor**. .. [\_](https://github.com/thisispiggy/my-wiki/tree/601ff771dc2fac1318ae8b59435ac8485628fd81/01%20Step%201/Endocrinology/ADH%20secretion%20stimulus/README.md)The primary stimulus for antidiuretic hormone (ADH) secretion is an **increase in serum osmolarity**. A loss of intracellular water from hypothalamic osmoreceptor neurons bathed by hyperosmolar blood will stimulate ADH release. Other factors that increase ADH secretion include: * **Pain/stress** * **Hypoglycemia** * **Nausea** * **Volume contraction** * **Nicotine and opiates** * **Angiotensin II**.. [\_](https://github.com/thisispiggy/my-wiki/tree/601ff771dc2fac1318ae8b59435ac8485628fd81/01%20Step%201/Endocrinology/ADH%20secretion%20inhibitor/README.md)The primary inhibitor of ADH secretion is a **decrease in serum osmolarity**. Other factors that decrease ADH secretion include: * **Alpha-agonists** * **Ethanol** * **Atrial natriuretic peptide** * **Cold**.. [\_](https://github.com/thisispiggy/my-wiki/tree/601ff771dc2fac1318ae8b59435ac8485628fd81/01%20Step%201/Endocrinology/ADH%20function/README.md)Antidiuretic hormone (ADH) has two primary functions: * **Regulate serum osmolarity** * **Maintain (increase) blood pressure**.. [\_](https://github.com/thisispiggy/my-wiki/tree/601ff771dc2fac1318ae8b59435ac8485628fd81/01%20Step%201/Endocrinology/ADH%20V2%20MOA/README.md)ADH increases water reabsorption by binding to V2 receptors on the capillary (basal) side of principal cells in the renal collecting duct: * ADH binding **activates adenylyl cyclase**, which increases cAMP and **activates protein kinase A.** * Activated **protein kinase A phosphorylates aquaporin-2-containing vesicles**, stimulating their transport and fusion with the luminal plasma membrane * The insertion of more aquaporin channels allows water to move rapidly from the tubular lumen into the collecting duct cell, reclaiming more water. * The result is an increase in blood volume and a decrease in plasma osmolarity. ![](https://f001.backblazeb2.com/file/wikiFiles/3m7jI9Q.jpg).. [\_](https://github.com/thisispiggy/my-wiki/tree/601ff771dc2fac1318ae8b59435ac8485628fd81/01%20Step%201/Endocrinology/ADH%20V1%20MOA/README.md)Vasopressin also causes vasoconstriction of arterioles through binding to **V1 receptors**, stimulating a IP3/Ca2+-mediated response. This vasoconstriction leads to a *direct increase in arterial pressure.* Note: this function can be remembered by the latter half of the hormones name -pressin *(remember, a pressor is any agent that increases blood pressure by stimulating constriction of blood vessels*)... [\_](https://github.com/thisispiggy/my-wiki/tree/601ff771dc2fac1318ae8b59435ac8485628fd81/01%20Step%201/Endocrinology/ADH%20effect%20on%20urea/README.md)Antidiuretic hormone also **increases the permeability of the inner medullary collecting duct to urea**. This increases the osmotic gradient created by the countercurrent multiplier, facilitating the production of concentrated urine (i.e. increasing urine osmolarity).. --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://thisispiggy.gitbook.io/my-wiki/01-step-1/endocrinology/07-pituitary-secretions.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.