Caption = Located at the base of the brain , the pituitary gland is protected by a bony structure called the sella turcica (also known as turkish saddle)of the sphenoid bone.
Caption2 = Median sagittal through the hypophysis of an adult monkey. Semidiagrammatic.
Precursor = neural and oral ectoderm , including Rathke’s pouch
Artery = superior hypophyseal artery , infundibular artery , prechiasmal artery , inferior hypophyseal artery , capsular artery , artery of the inferior cavernous sinus [cite journal | author = Gibo H, Hokama M, Kyoshima K, Kobayashi S | title = [Arteries to the pituitary] | journal = Nippon Rinsho | volume = 51 | issue = 10 | pages = 2550–4 | year = 1993 | pmid = 8254920]
MeshName = Pituitary+Gland
MeshNumber = A06.407.747
DorlandsPre = h_22
DorlandsSuf = 12439692
The pituitary gland, or hypophysis, is an endocrine gland about the size of a pea . It is a protrusion off the bottom of the hypothalamus at the base of the brain , and rests in a small, bony cavity ( sella turcica ) covered by a dural fold ( diaphragma sellae ). The pituitary fossa, in which the pituitary gland sits, is situated in the sphenoid bone in the middle cranial fossa at the base of the brain .
The pituitary gland secretes hormone s regulating homeostasis , including tropic hormone s that stimulate other endocrine glands . It is functionally connected to the hypothalamus by the median eminence .
Located at the base of the brain, the pituitary is functionally linked to the hypothalamus. It is composed of two lobes: the adenohypophysis and neurohypophysis . The adenohypophysis , also referred to as the anterior pituitary is divided into anatomical regions known as the pars tuberalis, pars intermedia, and pars distalis. The neurohypophysis , also referred to as the posterior pituitary. The pituitary is functionally linked to the hypothalamus by the pituitary stalk , whereby hypothalamic releasing factors are released and in turn stimulate the release of pituitary hormones.
Anterior pituitary (Adenohypophysis)
:main|Anterior pituitaryThe anterior pituitary synthesizes and secretes important endocrine hormones, such as ACTH, TSH, PRL, GH, endorphin s, FSH, and LH. These hormones are released from the anterior pituitary under the influence of hypothalamus . Hypothalamic hormones are secreted to the anterior lobe by way of a special capillary system, called the hypothalamic-hypophyseal portal system .it is developed from dorsalwall of pharynx(stomodial part) i.e called as ‘ruthke’s pouch’. they all transport by special nerve cells present in the hypothalamus.such nerve cells are located in various parts of hypothalamus & send their nerve fibre into median eminence & tubar cinerium(b/w ant. &post. lobe).
Posterior pituitary (Neurohypophysis)
The hormones secreted by the posterior pituitary are
* Oxytocin , where the majority is released from the paraventricular nucleus in the hypothalamus
* Antidiuretic hormone (ADH, also known as vasopressin and AVP, arginine vasopressin), the majority of which is released from the supraoptic nucleus in the hypothalamus
Oxytocin is one of the few hormones to create a positive feedback loop. For example, uterine contractions stimulate the release of oxytocin from the posterior pituitary, which in turn increases uterine contractions. This positive feedback loop continues until the baby is born.
There is also an intermediate lobe in many animals. For instance in fish it is believed to control physiological colour change. In adult humans it is just a thin layer of cells between the anterior and posterior pituitary. The intermediate lobe produces melanocyte-stimulating hormone (MSH), although this function is often (imprecisely) attributed to the anterior pituitary.
The pituitary hormones help control some of the following body processes:
* Blood pressure
* Some aspects of pregnancy and childbirth including stimulation of uterine contractions during childbirth
* Breast milk production
* Sex organ functions in both women and men
* Thyroid gland function
* The conversion of food into energy ( metabolism )
* Water and osmolarity regulation in the body
Disorders involving the pituitary gland include:
* Head and neck anatomy
* [http://www.umm.edu/endocrin/pitgland.htm The Pituitary Gland, from the UMM Endocrinology Health Guide]
* [http://instruction.cvhs.okstate.edu/Histology/HistologyReference/HREndoframe.htm Oklahoma State, Endocrine System]
* Pituitary apoplexy mimicking pituitary abscess [http://www.ispub.com/ostia/index.php?xmlPrinter=true&xmlFilePath=journals/ijns/vol4n1/pituitary.xml]
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Look at other dictionaries:
Pituitary gland — Pituitary Pi*tu i*ta*ry, a. [L. pituita phlegm, pituite: cf. F. pituitarie.] (Anat.) (a) Secreting mucus or phlegm; as, the pituitary membrane, or the mucous membrane which lines the nasal cavities. (b) Of or pertaining to the pituitary body; as … The Collaborative International Dictionary of English
pituitary gland — (also pituitary body) ► NOUN ▪ a pea sized gland attached to the base of the brain, important in controlling growth and development. ORIGIN Latin pituitarius secreting phlegm … English terms dictionary
pituitary gland — or pituitary body n. a small, oval endocrine gland attached by a stalk to the base of the brain and consisting of an anterior and a posterior lobe: it secretes hormones influencing body growth, metabolism, the activity of other endocrine glands,… … English World dictionary
pituitary gland — Anat. a small, somewhat cherry shaped double structure attached by a stalk to the base of the brain and constituting the master endocrine gland affecting all hormonal functions in the body, consisting of an anterior region (anterior pituitary or… … Universalium
Pituitary gland — The main endocrine gland. It is a small structure in the head. It is called the master gland because it produces hormones that control other glands and many body functions including growth. The pituitary consists of the anterior and posterior… … Medical dictionary
pituitary gland — noun the master gland of the endocrine system; located at the base of the brain (Freq. 2) • Syn: ↑pituitary, ↑pituitary body, ↑hypophysis • Derivationally related forms: ↑hypophysial (for: ↑ … Useful english dictionary
pituitary gland — UK [pɪˈtjuːɪt(ə)rɪ ˌɡlænd] / US [pɪˈtjuəterɪ ˌɡlænd] noun [countable] Word forms pituitary gland : singular pituitary gland plural pituitary glands medical the small organ at the base of your brain that produces the substances your body needs to… … English dictionary
pituitary gland — [[t]pɪtju͟ːɪtri glæ̱nd, AM tu͟ːɪteri [/t]] pituitary glands N COUNT: usu sing The pituitary gland or the pituitary is a gland that is attached to the base of the brain. It produces hormones which affect growth, sexual development, and other… … English dictionary
pituitary gland — pi|tu|i|tar|y gland [ pı tjuəteri ,glænd ] noun count the small organ at the base of your brain that produces the substances your body needs to control its growth and development. The pituitary gland is often simply called the pituitary … Usage of the words and phrases in modern English
pituitary gland — pitu′itary gland n. anat. a small, somewhat cherry shaped double lobed structure attached to the base of the brain, constituting the master endocrine gland affecting all hormonal functions of the body Compare anterior pituitary posterior… … From formal English to slang
Pituitary gland (Гипофиз)
The hypothalamus and pituitary gland function in a coordinated fashion to orchestrate many of the endocrine systems. The hypothalamic-pituitary unit regulates the functions of the thyroid, adrenal, and reproductive glands and also controls growth, milk production and ejection, and osmoregulation. It is important to visualize the anatomic relationships between the hypothalamus and the pituitary because these relationships underlie the functional connections between the glands.
The pituitary gland, which also is called the hypophysis, consists of a posterior lobe and an anterior lobe. The posterior lobe (or posterior pituitary) is also called the neurohypophysis. The anterior lobe (or anterior pituitary) is also called the adenohypophysis. The hypothalamus is connected to the pituitary gland by a thin stalk called the infundibulum. Functionally, the hypothalamus controls the pituitary gland by both neural and hormonal mechanisms (Fig. 9-9).
Figure 9–9 Schematic figure showing the relationship between the hypothalamus and the posterior and anterior lobes of the pituitary gland. Pink circles are posterior pituitary hormones; yellow circles are hypothalamic hormones; triangles are anterior pituitary hormones. ADH, Antidiuretic hormone; TRH, thyrotropin-releasing hormone; TSH, thyroid-stimulating hormone.
Relationship of the Hypothalamus to the Posterior Pituitary
The posterior lobe of the pituitary gland is derived from neural tissue. It secretes two peptide hormones, antidiuretic hormone (ADH) and oxytocin, which act on their respective target tissues—the kidney, the breast, and the uterus.
The connections between the hypothalamus and the posterior lobe of the pituitary are neural. In fact, the posterior pituitary is a collection of nerve axons whose cell bodies are located in the hypothalamus. Thus, the hormones secreted by the posterior lobe (ADH and oxytocin) are actually neuropeptides; in other words, they are peptides released from neurons.
The cell bodies of ADH- and oxytocin-secreting neurons are located in supraoptic and paraventricular nuclei within the hypothalamus. Although both hormones are synthesized in both nuclei, ADH is primarily associated with supraoptic nuclei and oxytocin is primarily associated with paraventricular nuclei.
Once synthesized in the cell bodies, the hormones (i.e., neuropeptides) are transported down the axons in neurosecretory vesicles and stored in bulbous nerve terminals in the posterior pituitary. When the cell body is stimulated, the neurosecretory vesicles are released from the nerve terminals by exocytosis and the secreted hormone enters nearby fenestrated capillaries. Venous blood from the posterior pituitary enters the systemic circulation, which delivers the hormones to their target tissues.
In summary, the relationship between the hypothalamus and the posterior pituitary is straightforward—a hormone-secreting neuron has its cell body in the hypothalamus and its axons in the posterior lobe of the pituitary.
Relationship of the Hypothalamus to the Anterior Pituitary
The anterior lobe of the pituitary gland is derived from primitive foregut. Unlike the posterior lobe, which is neural tissue, the anterior lobe is primarily a collection of endocrine cells. The anterior pituitary secretes six peptide hormones: thyroid-stimulating hormone (TSH), follicle-stimulating hormone (FSH), luteinizing hormone (LH), growth hormone, prolactin, and adrenocorticotropic hormone (ACTH).
The nature of the relationship between the hypothalamus and the anterior pituitary is both neural and endocrine (in contrast to the posterior lobe, which is only neural). The hypothalamus and anterior pituitary are linked directly by the hypothalamic-hypophysial portal blood vessels, which provide most of the blood supply to the anterior lobe.
There are both long and short hypophysial portal vessels, which are distinguished as follows: Arterial blood is delivered to the hypothalamus via the superior hypophysial arteries, which distribute the blood in a capillary network in the median eminence, called the primary capillary plexuses. These primary capillary plexuses converge to form the long hypophysial portal vessels, which travel down the infundibulum to deliver hypothalamic venous blood to the anterior lobe of the pituitary. A parallel capillary plexus forms from the inferior hypophysial arteries in the lower portion of the infundibular stem. These capillaries converge to form the short hypophysial portal vessels, which deliver blood to the anterior lobe of the pituitary. In summary, the blood supply of the anterior pituitary differs from that of other organs: Most of its blood supply is venous blood from the hypothalamus, supplied by the long and short hypophysial portal vessels.
There are two important implications of the portal blood supply to the anterior lobe of the pituitary: (1) The hypothalamic hormones can be delivered to the anterior pituitary directly and in high concentration, and (2) the hypothalamic hormones do not appear in the systemic circulation in high concentrations. The cells of the anterior pituitary, therefore, are the only cells in the body to receive high concentrations of the hypothalamic hormones.
The functional connections between the hypothalamus and the anterior lobe of the pituitary now can be understood in the context of the anatomic connections. Hypothalamic-releasing hormones and release-inhibiting hormones are synthesized in the cell bodies of hypothalamic neurons and travel down the axons of these neurons to the median eminence of the hypothalamus. Upon stimulation of these neurons, the hormones are secreted into the surrounding hypothalamic tissue and enter the nearby capillary plexus. The blood from these capillaries (now venous blood) drains into the hypophysial portal vessels and is delivered directly to the anterior lobe of the pituitary. There, the hypothalamic hormones act on the cells of the anterior lobe, where they stimulate or inhibit the release of the anterior pituitary hormones. The anterior pituitary hormones then enter the systemic circulation, which delivers them to their target tissues.
The hypothalamic-anterior pituitary relationship can be illustrated by considering the TRH–TSH–thyroid hormone system. TRH is synthesized in hypothalamic neurons and secreted in the median eminence of the hypothalamus, where it enters capillaries and then hypophysial portal vessels. It is delivered in this portal blood to the anterior lobe of the pituitary, where it stimulates TSH secretion. TSH enters the systemic circulation and is delivered to its target tissue, the thyroid gland, where it stimulates secretion of thyroid hormones.
A pituitary tumor is an abnormal growth in the pituitary gland. The pituitary is a small gland at the base of the brain. It regulates the body’s balance of many hormones.
Most pituitary tumors are noncancerous (benign). Up to 20% of people have pituitary tumors. Many of these tumors do not cause symptoms and are never diagnosed during the person’s lifetime.
The pituitary is part of the endocrine system. The pituitary helps control the release of hormones from other endocrine glands, such as the thyroid, sex glands (testes or ovaries), and adrenal glands. The pituitary also releases hormones that directly affect body tissues, such as bones and the breast milk glands. The pituitary hormones include:
- Adrenocorticotropic hormone (ACTH)
- Growth hormone (GH)
- Thyroid-stimulating hormone (TSH)
- Luteinizing hormone (LH) and follicle-stimulating hormone (FSH)
As a pituitary tumor grows, the normal hormone-releasing cells of the pituitary may be damaged. This results in the pituitary gland not producing enough of its hormones. This condition is called hypopituitarism.
The causes of pituitary tumors are unknown. Some tumors are caused by hereditary disorders such as multiple endocrine neoplasia I (MEN I).
The pituitary gland can be affected by other brain tumors that develop in the same part of the brain (skull base), resulting in similar symptoms.
Some pituitary tumors produce too much of one or more hormones. As a result, symptoms of one or more of the following conditions can occur:
- (thyroid gland makes too much of its hormones; this is an extremely rare condition of pituitary tumors) (body has a higher than normal level of the hormone cortisol) (abnormal growth due to higher than normal level of growth hormone during childhood) or acromegaly (higher than normal level of growth hormone in adults) and irregular or absent menstrual periods in women
- Decreased sexual function in men
Symptoms caused by pressure from a larger pituitary tumor may include:
- Changes in vision such as double vision, visual field loss (loss of peripheral vision), drooping eyelids or changes in color vision.
- Lack of energy.
- Nasal drainage of clear, salty fluid.
- Nausea and vomiting.
- Problems with the sense of smell.
- In rare cases, these symptoms occur suddenly and can be severe (pituitary apoplexy).
Exams and Tests
Your health care provider will perform a physical examination. The provider will note any problems with double vision and visual field, such as a loss of side (peripheral) vision or the ability to see in certain areas.
The exam will check for signs of too much cortisol (Cushing syndrome), too much growth hormone (acromegaly), or too much prolactin (prolactinoma).
Tests to check endocrine function may be ordered, including:
- Cortisol levels — dexamethasone suppression test, urine cortisol test, salivary cortisol test level
- Insulin growth factor-1 (IGF-1) level level
- Testosterone/estradiol levels
- Thyroid hormone levels — free T4 test, TSH test
Tests that help confirm the diagnosis include the following:
- Visual fields
- MRI of head
Surgery to remove the tumor is often needed, especially if the tumor is pressing on the nerves that control vision (optic nerves).
Most of the time, pituitary tumors can be surgically removed through the nose and sinuses. If the tumor cannot be removed this way, it is removed through the skull.
Radiation therapy may be used to shrink the tumor in people who cannot have surgery. It may also be used if the tumor returns after surgery.
In some cases, medicines are prescribed to shrink certain types of tumors.
These resources can provide more information on pituitary tumors:
- National Cancer Institute — www.cancer.gov/types/pituitary
- Pituitary Network Association — pituitary.org
- The Pituitary Society — www.pituitarysociety.org
If the tumor can be surgically removed, the outlook is fair to good, depending on whether the entire tumor is removed.
The most serious complication is blindness. This can occur if the optic nerve is seriously damaged.
The tumor or its removal may cause lifelong hormone imbalances. The affected hormones may need to be replaced, and you may need to take medicine for the rest of your life.
Tumors and surgery can sometimes damage the posterior pituitary (back part of the gland). This can lead to diabetes insipidus, a condition with symptoms of frequent urination and extreme thirst.
When to Contact a Medical Professional
Call your provider if you develop any symptoms of a pituitary tumor.
Tumor — pituitary; Pituitary adenoma
- Endocrine glands
- Pituitary gland
Dorsey JF, Salinas RD, Dang M, et al. Cancer of the central nervous system. In: Niederhuber JE, Armitage JO, Kastan MB, Doroshow JH, Tepper JE, eds. Abeloff’s Clinical Oncology. 6th ed. Philadelphia, PA: Elsevier; 2020:chap 63.
Melmed S, Kleinberg D. Pituitary masses and tumors. In: Melmed S, Polonsky KS, Larsen PR, Kronenberg HM, eds. Williams Textbook of Endocrinology. 13th ed. Philadelphia, PA: Elsevier; 2016:chap 9.
Pituitary gland (Гипофиз)
The pituitary gland is connected to the hypothalamus and secretes nine hormones that regulate body homeostasis.
Summarize the structure and function of the pituitary gland
- The pituitary gland, or hypophysis, is an endocrine gland about the size of a pea. Although located at the base of the brain and often considered to be part of the brain, the pituitary gland is in fact a separate organ, and is not part of the brain.
- The pituitary gland is divided into two parts, the anterior pituitary and the posterior pituitary. The anterior pituitary receives signalling molecules from the hypothalamus, and in response, synthesizes and secretes seven hormones.
- The posterior pituitary does not produce any hormones of its own; instead, it stores and secretes two hormones made in the hypothalamus.
- pituitary gland: An endocrine gland, about the size of a pea, that sits in a small, bony cavity at the base of the brain whose secretions control the other endocrine glands and influence growth, metabolism, and maturation.
- hypothalamus: A region of the forebrain located below the thalamus, forming the basal portion of the diencephalon, and functioning to regulate body temperature, some metabolic processes, and governing the autonomic nervous system.
The pituitary gland, or hypophysis, is an endocrine gland about the size of a pea. Although located at the base of the brain and often considered to be part of the brain, the pituitary gland is in fact a separate organ. It protrudes off the bottom of the hypothalamus at the base of the brain, and rests in a small, bony cavity.
Pituitary location: The location of pituitary gland in the human brain.
The pituitary is functionally connected to the hypothalamus by a small tube called the infundibular stem, or, pituitary stalk. The pituitary gland secretes hormones that regulate homeostasis.
The pituitary gland is divided into two parts, the anterior pituitary and the posterior pituitary.
- The anterior pituitary receives signaling molecules from the hypothalamus, and in response, synthesizes and secretes seven important hormones including thyroid-stimulating hormone and growth hormone.
- The posterior pituitary does not produce any hormones of its own, rather, it stores and secretes two hormones made in the hypothalamus— oxytocin and
The pituitary gland: In this image, the pituitary gland is referred to by its other name, the hypophysis.
Control of the Pituitary Gland by the Hypothalamus
The pituitary gland consists of the anterior pituitary and the posterior pituitary.
Explain how the hypothalamus controls the pituitary gland
- While the pituitary gland is known as the master endocrine gland, both of its lobes are under the control of the hypothalamus: the anterior pituitary receives its signals from the parvocellular neurons, and the posterior pituitary receives its signals from the magnocellular neurons.
- The pituitary gland is connected by a system of blood vessels to the hypothalamus. This system of blood vessels is known as the hypophyseal portal system, and it allows endocrine communication between the two structures.
- The mechanism for hormone transport via hypothalamoportal vessels involves cells that are regulated by different nuclei in the hypothalamus; for instance, neurons that release neurotransmitters as hormones in the connective link between the pituitary and the brain.
- pituitary gland: An endocrine gland, about the size of a pea, that sits in a small, bony cavity at the base of the brain whose secretions control the other endocrine glands and influence growth, metabolism, and maturation.
- hypothalamus: A region of the forebrain located below the thalamus, forming the basal portion of the diencephalon, that regulates body temperature, some metabolic processes, and governs the autonomic nervous system.
- hypophyseal portal system: The system of blood vessels that link the hypothalamus and the anterior pituitary in the brain.
The pituitary gland consists of two components: the anterior pituitary and the posterior pituitary, and is functionally linked to the hypothalamus by the pituitary stalk (also named the infundibular stem, or simply the infundibulum).
Whilst the pituitary gland is known as the master endocrine gland, both of the lobes are under the control of the hypothalamus: the anterior pituitary receives its signals from the parvocellular neurons, and the posterior pituitary receives its signals from magnocellular neurons.
The anterior lobe of the pituitary receives
hypothalamic-releasing hormones from the hypothalamus that bind with receptors on endocrine cells in the anterior pituitary that regulate the release of adrenal hormones into the circulatory system. Hormones from the hypothalamus are rapidly degraded in the anterior pituitary, which prevents them from entering the circulatory system.
The posterior lobe of the pituitary gland develops as an extension of the hypothalamus. As such, it is not capable of producing its own hormones; instead, it stores hypothalamic hormones for later release into the systemic circulation.
Pituitary gland: The anterior and posterior lobes of the pituitary (hypophysis) gland are shown.
The Anterior Pituitary
The anterior pituitary secretes seven hormones that regulate several physiological processes, including stress, growth, and reproduction.
Identify the location and the hormones produced by the anterior pituitary
- A major organ of the endocrine system, the anterior pituitary, also called the adenohypophysis, is the glandular, anterior lobe of the pituitary gland.
- The anterior pituitary regulates several physiological processes, including stress, growth, reproduction, and lactation.
- The anterior pituitary gland secretes 7 hormones: follicle -stimulating hormone, luteinizing horomone, adrenocorticotropic horomone, thyroid -stimulating horomone, prolactin, endorphins, and growth hormone.
- anterior pituitary gland: A major organ of the endocrine system that regulates several physiological processes including stress, growth, reproduction, and lactation.
A major organ of the endocrine system, the anterior pituitary (also called the adenohypophysis) is the glandular, anterior lobe of the pituitary gland. The anterior pituitary regulates several physiological processes including stress, growth, reproduction, and lactation.
Its regulatory functions are achieved through the secretion of various peptide hormones that act on target organs including the adrenal gland, liver, bone, thyroid gland, and gonads. The anterior pituitary itself is regulated by the hypothalamus and by negative feedback from these target organs.
Anatomy of the Anterior Pituitary Gland
The fleshy, glandular anterior pituitary is distinct from the neural composition of the posterior pituitary. The anterior pituitary is composed of multiple parts:
- Pars distalis: This is the distal part that comprises the majority of the anterior pituitary; it is where most pituitary hormone production occurs.
- Pars tuberalis: This is the tubular part that forms a sheath that extends up from the pars distalis and wraps around the pituitary stalk. Its function is poorly understood.
- Pars intermedia: This is the intermediate part that sits between the pars distalis and the posterior pituitary and is often very small in humans.
Major Hormones Secreted by the Anterior Pituitary Gland
- Adrenocorticotropic hormone (ACTH), is a polypeptide whose target is the adrenal gland. The effects of ACTH are upon secretion of glucocorticoid, mineralocorticoids, and sex corticoids.
- Beta-endorphin is a polypeptide that effects the opioid receptor, whose effects include the inhibition of the perception of pain.
- Thyroid-stimulating hormone is a glycoprotein hormone that affects the thyroid gland and the secretion of thyroid hormones.
- Follicle-stimulating hormone is a glycoprotein hormone that targets the gonads and effects the growth of the reproductive system.
- Luteinizing hormone is a glycoprotein hormone that targets the gonads to effect sex-hormone production.
- Growth hormone is a polypeptide hormone that targets the liver and adipose tissue and promotes growth through lipid and carbohydrate metabolism.
- Prolactin is a polypeptide hormone whose target is the ovaries and mammary glands. Prolactin influences the secretion of estrogen/progesterone and milk production.
Hormone secretion from the anterior pituitary gland is regulated by hormones secreted by the hypothalamus. Neuroendocrine neurons in the hypothalamus project axons to the median eminence, at the base of the brain. At this site, these neurons can release substances into the small blood vessels that travel directly to the anterior pituitary gland (the hypothalamo-hypophysial portal vessels).
The anterior pituitary: The anterior pituitary, in yellow, is linked to the hypothalamus by a portal system. The hypothalamus releases signaling molecules that incite the anterior pituitary to produce hormones.
The Posterior Pituitary
The posterior pituitary secretes two important endocrine hormones—oxytocin and antidiuretic hormone.
Identify the location of the posterior pituitary and the hormones associated with it
- The posterior pituitary (or neurohypophysis) comprises the posterior lobe of the pituitary gland and is part of the endocrine system.
- Hormones known as posterior pituitary hormones are synthesized by the hypothalamus, and include oxytocin and antidiuretic hormone.
- The hormones are then stored in neurosecretory vesicles (Herring bodies) before being secreted by the posterior pituitary into the bloodstream.
- oxytocin: A hormone that stimulates contractions during labor.
- posterior pituitary: The posterior pituitary (or neurohypophysis) comprises the posterior lobe of the pituitary gland and is part of the endocrine system. Despite its name, the posterior pituitary gland is not a true gland; rather, it is largely a collection of axonal projections from the hypothalamus that terminate behind the anterior pituitary gland.
- Antidiuretic hormone: A hormone that stimulates water re-absorption in the kidneys.
Posterior Pituitary Gland
Pituitary: Pituitary gland representation.
The posterior pituitary (or neurohypophysis) comprises the posterior lobe of the pituitary gland and is part of the endocrine system. Despite its name, the posterior pituitary gland is not a gland; rather, it is largely a collection of axonal projections from the hypothalamus that terminate behind the anterior pituitary gland.
The posterior pituitary consists mainly of neuronal projections ( axons ) extending from the supraoptic and paraventricular nuclei of the hypothalamus. These axons release peptide hormones into the capillaries of the hypophyseal circulation. These are then stored in neurosecretory vesicles (Herring bodies) before being secreted by the posterior pituitary into the systemic bloodstream.
Anatomy of the Posterior Pituitary Gland
The posterior pituitary is derived from the hypothalamus and is distinct from the more fleshy, vascularized anterior lobe. The posterior pituitary is composed of two parts:
- The pars nervosa, also called the neural lobe or posterior lobe, constitutes the majority of the posterior pituitary and is the storage site of oxytocin and vasopressin.
- The infundibular stalk, also known as the infundibulum or pituitary stalk, bridges the hypothalamic and hypophyseal systems.
Major Hormones Secreted by the Posterior Pituitary Gland
The posterior pituitary stores two hormones secreted by the hypothalamus for later release:
Pituitary gland (Гипофиз)
Overview of Hypothalamic and Pituitary Hormones
The pituitary gland is often portrayed as the «master gland» of the body. Such praise is justified in the sense that the anterior and posterior pituitary secrete a battery of hormones that collectively influence all cells and affect virtually all physiologic processes.
The pituitary gland may be king, but the power behind the throne is clearly the hypothalamus. As alluded to in the last section, some of the neurons within the hypothalamus — neurosecretory neurons — secrete hormones that strictly control secretion of hormones from the anterior pituitary. The hypothalamic hormones are referred to as releasing hormones and inhibiting hormones , reflecting their influence on anterior pituitary hormones.
Hypothalamic releasing and inhibiting hormones are carried directly to the anterior pituitary gland via hypothalamic-hypophyseal portal veins. Specific hypothalamic hormones bind to receptors on specific anterior pituitary cells, modulating the release of the hormone they produce.
As an example, thyroid-releasing hormone from the hypothalamus binds to receptors on anterior pituitary cells called thyrotrophs, stimulating them to secrete thyroid-stimulating hormone or TSH. The anterior pituitary hormones enter the systemic circulation and bind to their receptors on other target organs. In the case of TSH, the target organ is the thyroid gland.
Clearly, robust control systems must be in place to prevent over or under-secretion of hypothalamic and anterior pituitary hormones. A prominent mechanism for control of the releasing and inhibiting hormones is negative feedback. Details on the control of specific hypothalamic and anterior pituitary hormones is presented in the discussions of those hormones.
The following table summarizes the major hormones synthesized and secreted by the pituitary gland, along with summary statements about their major target organs and physiologic effects. Keep in mind that summaries are just that, and ongoing research continues to delineate additional, sometimes very important effects.
|Hormone||Major target organ(s)||Major Physiologic Effects|
|Growth hormone||Liver, adipose tissue||Promotes growth (indirectly), control of protein, lipid and carbohydrate metabolism|
|Thyroid-stimulating hormone||Thyroid gland||Stimulates secretion of thyroid hormones|
|Adrenocorticotropic hormone||Adrenal gland (cortex)||Stimulates secretion of glucocorticoids|
|Prolactin||Mammary gland||Milk production|
|Luteinizing hormone||Ovary and testis||Control of reproductive function|
|Follicle-stimulating hormone||Ovary and testis||Control of reproductive function|
|Antidiuretic hormone||Kidney||Conservation of body water|
|Oxytocin||Ovary and testis||Stimulates milk ejection and uterine contractions|
A final point to be made is that individual cells within the anterior pituitary secrete a single hormone (or possibly two in some cases). Thus, the anterior pituitary contains at least six distinctive endocrinocytes.
The cells that secrete thyroid-stimulating hormone do not also secrete growth hormone, and they have receptors for thyroid-releasing hormone, not growth hormone-releasing hormone. The image below is of a section of canine anterior pituitary that was immunologically stained for luteinizing hormone (black stain) and prolactin (purple stain). The unstained cells in the image are those that secrete the other pituitary hormones.
Anatomy of the Hypothalamus and Pituitary Gland