Endocrine glands are glands of the endocrine system that secrete their products, hormones, directly into the blood rather than through a duct. The major glands of the endocrine system include the pineal gland, pituitary gland, pancreas, ovaries, testes, thyroid gland, parathyroid gland, hypothalamus and adrenal glands. The hypothalamus and pituitary gland are neuroendocrine organs.
|FMA||9602 71653, 9602|
The pituitary gland hangs from the base of the brain by the pituitary stalk, and is enclosed by bone. It consists of a hormone-producing glandular portion the anterior pituitary and a neural portion the posterior pituitary, which is an extension of the hypothalamus. The hypothalamus regulates the hormonal output of the anterior pituitary and creates two hormones that it exports to the posterior pituitary for storage and later release.
Four of the six anterior pituitary hormones are tropic hormones that regulate the function of other endocrine organs. Most anterior pituitary hormones exhibit a diurnal rhythm of release, which is subject to modification by stimuli influencing the hypothalamus.
Somatotropic hormone or growth hormone (GH) is an anabolic hormone that stimulates growth of all body tissues especially skeletal muscle and bone. It may act directly, or indirectly via insulin-like growth factors (IGFs). GH mobilizes fats, stimulates protein synthesis, and inhibits glucose uptake and metabolism. Secretion is regulated by growth hormone releasing hormone (GHRH) and growth hormone inhibiting hormone (GHIH), or somatostatin. Hypersecretion causes gigantism in children and acromegaly in adults; hyposecretion in children causes pituitary dwarfism.
Thyroid-stimulating hormone (TSH) promotes normal development and activity of the thyroid gland. Thyrotropin-releasing hormone (TRH) stimulates its release; negative feedback of thyroid hormone inhibits it.
Adrenocorticotropic hormone (ACTH) stimulates the adrenal cortex to release corticosteroids. ACTH release is triggered by corticotropin-releasing hormone (CRH) and inhibited by rising glucocorticoid levels.
The gonadotropins—follicle-stimulating hormone (FSH) and luteinizing hormone (LH) regulate the functions of the gonads in both sexes. FSH stimulates sex cell production; LH stimulates gonadal hormone production. Gonadotropin levels rise in response to gonadotropin-releasing hormone (GnRH). Negative feedback of gonadal hormones inhibits gonadotropin release.
The neurohypophysis stores and releases two hypothalamic hormones:
The thyroid gland is located at the front of the neck, in front of the thyroid cartilage, and is shaped like a butterfly, with two wings connected by a central isthmus. Thyroid tissue consists of follicles with stored protein called colloid, containing thyroglobulin, a precursor to other thyroid hormones, which are manufactured within the colloid.
The thyroid hormones increase the rate of cellular metabolism, and include thyroxine (T4) and triiodothyronine (T3). Secretion is stimulated by the hormone TSH, secreted by the anterior pituitary. When thyroid levels are high, there is negative feedback that decreases the amount of TSH secreted. Most T4 is converted to T3 (a more active form) in the target tissues.
Calcitonin, produced by the parafollicular cells of the thyroid gland in response to rising blood calcium levels, depresses blood calcium levels by inhibiting bone matrix resorption and enhancing calcium deposit in bone.
The parathyroid glands, of which there are 4-6, are found on the back of the thyroid glands, and secrete parathyroid hormone (PTH), which causes an increase in blood calcium levels by targeting bone, the intestine, and the kidneys. PTH is the antagonist of calcitonin. PTH release is triggered by falling blood calcium levels and is inhibited by rising blood calcium levels.
The adrenal glands are located above the kidneys in humans and in front of the kidneys in other animals. The adrenal glands produce a variety of hormones including adrenaline and the steroids aldosterone and cortisol. It controls the behaviour during crisis and emotional situations. It stimulates the heart and its conducting tissues and metabolic processes.
The pancreas, located in the abdomen, below and behind the stomach, is both an exocrine and an endocrine gland. The alpha and beta cells are the endocrine cells in the pancreatic islets that release insulin and glucagon and smaller amounts of other hormones into the blood. Insulin and glucagon influence blood sugar levels. Glucagon is released when blood glucose level is low, and stimulates the liver to release glucose into the blood. Insulin increases the rate of glucose uptake and metabolism by most body cells.
The ovaries of the female, located in the pelvic cavity, release two main hormones. Secretion of oestrogens by the ovarian follicles begins at puberty under the influence of FSH. Estrogens stimulate maturation of the female reproductive system and development of the secondary sexual characteristics. Progesterone is released in response to high blood levels of LH. It works with estrogens in establishing the menstrual cycle.
The testes of the male begin to produce testosterone at puberty in response to LH. Testosterone promotes maturation of the male reproductive organs, development of secondary sex characteristics such as beard, hoarse voice, etc. and production of sperm by the testes.
The pineal gland is located in the diencephalon of the brain. It primarily releases melatonin, which influences daily rhythms and may have an antigonadotropic effect in humans. It may also influence the melanotropes and melanocytes located in the skin.
Many body organs not normally considered endocrine organs contain isolated cell clusters that secrete hormones. Examples include the heart (atrial natriuretic peptide); gastrointestinal tract organs (gastrin, secretin, and others); the placenta (hormones of pregnancy—estrogen, progesterone, and others); the kidneys (erythropoietin and renin); the thymus; skin (cholecalciferol); and adipose tissue (leptin and resistin).
Endocrine glands derive from all three germ layers.
The natural decrease in function of the female’s ovaries during late middle age results in menopause. The efficiency of all endocrine glands seems to decrease gradually as aging occurs. This leads to a generalized increase in the incidence of diabetes mellitus and a lower metabolic rate.
Local chemical messengers, not generally considered part of the endocrine system, include autocrines, which act on the cells that secrete them, and paracrines, which act on a different cell type nearby.
The ability of a target cell to respond to a hormone depends on the presence of receptors, within the cell or on its plasma membrane, to which the hormone can bind.
Hormone receptors are dynamic structures. Changes in number and sensitivity of hormone receptors may occur in response to high or low levels of stimulating hormones.
Blood levels of hormones reflect a balance between secretion and degradation/excretion. The liver and kidneys are the major organs that degrade hormones; breakdown products are excreted in urine and feces.
Hormone half-life and duration of activity are limited and vary from hormone to hormone.
Interaction of hormones at target cells Permissiveness is the situation in which a hormone cannot exert its full effects without the presence of another hormone.
Synergism occurs when two or more hormones produce the same effects in a target cell and their results are amplified.
Antagonism occurs when a hormone opposes or reverses the effect of another hormone.
The endocrine glands belong to the body's control system. The hormones which they produce help to regulate the functions of cells and tissues throughout the body. Endocrine organs are activated to release their hormones by humoral, neural or hormonal stimuli. Negative feedback is important in regulating hormone levels in the blood.
The nervous system, acting through hypothalamic controls, can in certain cases override or modulate hormonal effects.
Endocrine disease is characterized by irregulated hormone release (a productive pituitary adenoma), inappropriate response to signaling (hypothyroidism), lack of a gland (diabetes mellitus type 1, diminished erythropoiesis in chronic renal failure), or structural enlargement in a critical site such as the thyroid (toxic multinodular goitre). Hypofunction of endocrine glands can occur as a result of loss of reserve, hyposecretion, agenesis, atrophy, or active destruction. Hyperfunction can occur as a result of hypersecretion, loss of suppression, hyperplastic or neoplastic change, or hyperstimulation.
Endocrinopathies are classified as primary, secondary, or tertiary. Primary endocrine disease inhibits the action of downstream glands. Secondary endocrine disease is indicative of a problem with the pituitary gland. Tertiary endocrine disease is associated with dysfunction of the hypothalamus and its releasing hormones.
As the thyroid, and hormones have been implicated in signaling distant tissues to proliferate, for example, the estrogen receptor has been shown to be involved in certain breast cancers. Endocrine, paracrine, and autocrine signaling have all been implicated in proliferation, one of the required steps of oncogenesis.
Other common diseases that result from endocrine dysfunction include Addison’s disease, Cushing’s disease and Grave’s disease. Cushing's disease and Addison's disease are pathologies involving the dysfunction of the adrenal gland. Dysfunction in the adrenal gland could be due to primary or secondary factors and can result in hypercortisolism or hypocortisolism . Cushing’s disease is characterized by the hypersecretion of the adrenocorticotropic hormone (ACTH) due to a pituitary adenoma that ultimately causes endogenous hypercortisolism by stimulating the adrenal glands. Some clinical signs of Cushing’s disease include obesity, moon face, and hirsutism. Addison's disease is an endocrine disease that results from hypocortisolism caused by adrenal gland insufficiency. Adrenal insufficiency is significant because it is correlated with decreased ability to maintain blood pressure and blood sugar, a defect that can prove to be fatal.
Graves' disease involves the hyperactivity of the thyroid gland which produces the T3 and T4 hormones. Graves' disease effects range from excess sweating, fatigue, heat intolerance and high blood pressure to swelling of the eyes that causes redness, puffiness and in rare cases reduced or double vision.
Hyperparathyroidism results in hypercalcaemia and its effects and in extreme bone wasting. Hypoparathyroidism leads to hypocalcaemia, evidenced by tetany seizure and respiratory paralysis. Hyposecretion of insulin results in diabetes mellitus; cardinal signs are polyuria, polydipsia, and polyphagia.
APG is an abbreviation with several different meanings:
Aberdeen Proving Ground, a United States Army installation in Aberdeen, Maryland, also
Phillips Army Airfield, the airfield of the above, from its IATA airport code
Aboriginal Provisional Government, Indigenous Australian independence movement
Alkyl polyglycoside, a class of surfactants
Algemene Pensioen Groep, a Netherlands-based pension fund established under the Algemene Ouderdoms Wet
Ambulatory Patient Group
André-Pierre Gignac, a French footballer who plays for Liga MX club Tigres UANL and the France national team
Android Privacy Guard, an implementation of Pretty Good Privacy for the Android operating system
Angiosperm Phylogeny Group, a collaboration of botanists, publishing classification systems of flowering plants
Annealed pyrolytic graphite, a thermally conductive form of synthetic graphite
Anterior Pituitary Gland, an endocrine gland
APG Airlines, a French airline based in Cannes.
Arc Pair Grammar
Asia/Pacific Group on Money Laundering, the FATF-style regional body for the Asia and Pacific region
Aspley Guise railway station, from its National Rail code
Association of Professional Genealogists
Associated petroleum gas
Atlas of Peculiar Galaxies
Austrian Power Grid, Austrian electric power transmission company
Automated Password Generator, a software generating password
Automatic platform gate, a safety facility preventing awaiting passenger falling from station platform to rail tracks
Assists per game, in basketballAcinus
An acinus (; plural, acini; adjective, acinar or acinous) refers to any cluster of cells that resembles a many-lobed "berry", such as a raspberry (acinus is Latin for "berry"). The berry-shaped termination of an exocrine gland, where the secretion is produced, is acinar in form, as is the alveolar sac containing multiple alveoli in the lungs.Adenocarcinoma
Adenocarcinoma (; plural adenocarcinomas or adenocarcinomata ) is a type of cancerous tumor that can occur in several parts of the body. It is defined as neoplasia of epithelial tissue that has glandular origin, glandular characteristics, or both. Adenocarcinomas are part of the larger grouping of carcinomas, but are also sometimes called by more precise terms omitting the word, where these exist. Thus invasive ductal carcinoma, the most common form of breast cancer, is adenocarcinoma but does not use the term in its name—however, esophageal adenocarcinoma does to distinguish it from the other common type of esophageal cancer, esophageal squamous cell carcinoma. Several of the most common forms of cancer are adenocarcinomas, and the various sorts of adenocarcinoma vary greatly in all their aspects, so that few useful generalizations can be made about them.
In the most specific usage (narrowest sense), the glandular origin or traits are exocrine; endocrine gland tumors, such as a VIPoma, an insulinoma, or a pheochromocytoma, are typically not referred to as adenocarcinomas but rather are often called neuroendocrine tumors. Epithelial tissue sometimes includes, but is not limited to, the surface layer of skin, glands, and a variety of other tissue that lines the cavities and organs of the body. Epithelial tissue can be derived embryologically from any of the germ layers (ectoderm, endoderm, or mesoderm). To be classified as adenocarcinoma, the cells do not necessarily need to be part of a gland, as long as they have secretory properties. Adenocarcinoma is the malignant counterpart to adenoma, which is the benign form of such tumors. Sometimes adenomas transform into adenocarcinomas, but most do not.
Well differentiated adenocarcinomas tend to resemble the glandular tissue that they are derived from, while poorly differentiated adenocarcinomas may not. By staining the cells from a biopsy, a pathologist can determine whether the tumor is an adenocarcinoma or some other type of cancer. Adenocarcinomas can arise in many tissues of the body owing to the ubiquitous nature of glands within the body, and, more fundamentally, to the potency of epithelial cells. While each gland may not be secreting the same substance, as long as there is an exocrine function to the cell, it is considered glandular and its malignant form is therefore named adenocarcinoma.Corpus allatum
In insect physiology, the corpus allatum (plural: corpora allata) is an endocrine gland which generates juvenile hormone; as such, it plays a crucial role in metamorphosis. Surgical removal of the corpora allata (an allatectomy) can cause an immature larva to pupate at its next molt, resulting in a miniature adult. Similarly, transplantation of corpora allata from a young larva to a fully mature larva can greatly extend the larval stage, resulting in an equivalent to gigantism.In many Diptera species, the corpus allatum is fused with the corpus cardiacum, forming a "ring gland", also known as Weismann's ring.In Lepidoptera species, the corpus allatum acts as a release site for prothoracicotropic hormone which is generated by the brain.Duct (anatomy)
In anatomy and physiology, a duct is a circumscribed channel leading from an exocrine gland or organ.Endocrine disease
Endocrine diseases are disorders of the endocrine system. The branch of medicine associated with endocrine disorders is known as endocrinology.Endocrine gland neoplasm
An endocrine gland neoplasm is a neoplasm affecting one or more glands of the endocrine system.
Pituitary adenomaThe most common form is thyroid cancer.Condition such as pancreatic cancer or ovarian cancer can be considered endocrine tumors, or classified under other systems.
Pinealoma is often grouped with brain tumors because of its location.Gland
A gland is a group of cells in an animal's body that synthesizes substances (such as hormones) for release into the bloodstream (endocrine gland) or into cavities inside the body or its outer surface (exocrine gland).Martin Benno Schmidt
Martin Benno Schmidt (23 August 1863 – 27 November 1949) was a German pathologist born in Leipzig.
He spent several years as an assistant at the University of Strasbourg, where he worked under Friedrich Daniel von Recklinghausen (1833-1910). In 1906 he became a professor of pathology at the medical academy in Düsseldorf, and afterwards worked as a pathologist in Zurich and Marburg. In 1913 he succeeded Richard Kretz (1865-1920) as professor of pathology at the University of Würzburg, a position he maintained until his retirement in 1934.
Schmidt specialized in pathological investigations of bone disorders such as rickets, osteogenesis imperfecta, and osteomalacia. He is remembered for his description of autoimmune polyendocrine syndrome, type II, a disease characterized by autoimmune activity against more than one endocrine gland. This condition is sometimes referred to as "Schmidt's syndrome". He also performed important studies involving iron metabolism.Neurosteroid
Neurosteroids, also known as neuroactive steroids, are endogenous or exogenous steroids that rapidly alter neuronal excitability through interaction with ligand-gated ion channels and other cell surface receptors. The term neurosteroid was coined by the French physiologist Étienne-Émile Baulieu and refers to steroids synthesized in the brain. The term, neuroactive steroid refers to steroids that can be synthesized in the brain, or are synthesized by an endocrine gland, that then reach the brain through the bloodstream and have effects on brain function. The term neuroactive steroids was first coined in 1992 by Steven Paul and Robert Purdy. In addition to their actions on neuronal membrane receptors, some of these steroids may also exert effects on gene expression via nuclear steroid hormone receptors. Neurosteroids have a wide range of potential clinical applications from sedation to treatment of epilepsy and traumatic brain injury. Ganaxolone, a synthetic analog of the endogenous neurosteroid allopregnanolone, is under investigation for the treatment of epilepsy.Ovary
The ovary is an organ found in the female reproductive system that produces an ovum. When released, this travels down the fallopian tube into the uterus, where it may become fertilised by a sperm. There is an ovary (from Latin ovarium, meaning 'egg, nut') found on the left and right sides of the body. The ovaries also secrete hormones that play a role in the menstrual cycle and fertility. The ovary progresses through many stages beginning in the prenatal period through menopause. It is also an endocrine gland because of the various hormones that it secretes.Pineal gland
The pineal gland is a small endocrine gland in the brain of animals with backbones. The pineal gland produces melatonin, a serotonin-derived hormone which modulates sleep patterns in both circadian and seasonal cycles. The shape of the gland resembles a pine cone from which it derived its name. The pineal gland is located in the epithalamus, near the center of the brain, between the two hemispheres, tucked in a groove where the two halves of the thalamus join. It is also called the conarium, kônarion or epiphysis cerebri. The pineal gland is included among a group of specialized neuroendocrine brain structures called the circumventricular organs.Nearly all vertebrate species possess a pineal gland. The most important exception is a primitive vertebrate, the hagfish. Even in the hagfish, however, there may be a "pineal equivalent" structure in the dorsal diencephalon. The lancelet Branchiostoma lanceolatum, the nearest existing relative to vertebrates, also lacks a recognizable pineal gland. The lamprey (another primitive vertebrate), however, does possess one. A few more developed vertebrates lost pineal glands over the course of their evolution.The results of various scientific research in evolutionary biology, comparative neuroanatomy and neurophysiology, have explained the phylogeny of the pineal gland in different vertebrate species. From the point of view of biological evolution, the pineal gland represents a kind of atrophied photoreceptor. In the epithalamus of some species of amphibians and reptiles, it is linked to a light-sensing organ, known as the parietal eye, which is also called the pineal eye or third eye.René Descartes believed the human pineal gland to be the "principal seat of the soul". Academic philosophy among his contemporaries considered the pineal gland as a neuroanatomical structure without special metaphysical qualities; science studied it as one endocrine gland among many.Pineal gland cyst
A pineal gland cyst is a usually benign (non-malignant) cyst in the pineal gland, a small endocrine gland in the brain. Historically, these fluid-filled bodies appeared on 1-4% of magnetic resonance imaging (MRI) brain scans, but were more frequently diagnosed at death, seen in 4-11% of autopsies. A 2007 study by Pu et al. found a frequency of 23% in brain scans (with a mean diameter of 4.3 mm).It was once believed that smaller cysts (less than 5.0 mm) were usually asymptomatic, but for larger cysts (greater than 5.0 mm), symptoms could include headache, unexpected seizures, visual disturbances, memory loss, cognitive decline, muscle fasciculations, nausea, weakness, fatigue, light sensitivity, tinnitus, circadian rhythm dysfunction, or hydrocephalus if the cyst impinged on the superior colliculi or caused obstruction of the cerebral aqueduct. Newer research shows that the size of the cyst does not necessarily correlate to the presence of symptoms. In some cases, it will need to be removed before life-threatening situations occur. The usual size a pineal cyst might start to cause symptoms Varies but usually 7mm and up.Despite the pineal gland being in the center of the brain, due to recent advancements in endoscopic medicine, endoscopic brain surgery to drain and/or remove the cyst can be done with the patient spending 5-10 nights in the hospital, and being fully recovered in weeks, rather than a year, as is the case with open-skull brain surgery.The National Organization for Rare Disorders states that pineal cysts larger than 5.0 mm are "rare findings" and are possibly symptomatic. If narrowing of the cerebral aqueduct occurs, many neurological symptoms may exist, including headaches, vertigo, nausea, muscle fasciculations, eye sensitivity, and ataxia. Continued monitoring of the cyst might be recommended to monitor its growth, and surgery may be necessary.Pituitary gland
In vertebrate anatomy, the pituitary gland, or hypophysis, is an endocrine gland about the size of a pea and weighing 0.5 grams (0.018 oz) in humans. It is a protrusion off the bottom of the hypothalamus at the base of the brain. The hypophysis rests upon the hypophysial fossa of the sphenoid bone in the center of the middle cranial fossa and is surrounded by a small bony cavity (sella turcica) covered by a dural fold (diaphragma sellae). The anterior pituitary (or adenohypophysis) is a lobe of the gland that regulates several physiological processes (including stress, growth, reproduction, and lactation). The intermediate lobe synthesizes and secretes melanocyte-stimulating hormone. The posterior pituitary (or neurohypophysis) is a lobe of the gland that is functionally connected to the hypothalamus by the median eminence via a small tube called the pituitary stalk (also called the infundibular stalk or the infundibulum).
Hormones secreted from the pituitary gland help in controlling growth, blood pressure, energy management, all functions of the sex organs, thyroid glands and metabolism as well as some aspects of pregnancy, childbirth, nursing, water/salt concentration at the kidneys, temperature regulation and pain relief.Prokineticin receptor
The prokineticin receptor is a G protein-coupled receptor which binds the peptide hormone prokineticin. There are two variants each encoded by a different gene (PROKR1, PROKR2). These receptors mediate gastrointestinal smooth muscle contraction and angiogenesis.Prokineticin receptor 1
Prokineticin receptor 1, also known as PKR1, is a human protein encoded by the PROKR1 gene.Prokineticin receptor 2
Prokineticin receptor 2 (PKR2), is a G protein-coupled receptor encoded by the PROKR2 gene in humans.TAC4
Tachykinin-4 is a protein that in humans is encoded by the TAC4 gene.This gene is a member of the tachykinin family of neurotransmitter-encoding genes. Tachykinin proteins are cleaved into small, secreted peptides that activate members of a family of receptor proteins. The products of this gene preferentially activate tachykinin receptor 1, and are thought to regulate peripheral endocrine and paracrine functions including blood pressure, the immune system, and endocrine gland secretion. The products of this gene lack a dibasic cleavage site found in other tachykinin proteins. Consequently, the nature of the cleavage products generated in vivo remains to be determined. Multiple transcript variants encoding different isoforms have been found for this gene.