Endocrinology
Encyclopedia
Endocrinology is a branch of biology and medicine dealing with the endocrine system
Endocrine system
In physiology, the endocrine system is a system of glands, each of which secretes a type of hormone directly into the bloodstream to regulate the body. The endocrine system is in contrast to the exocrine system, which secretes its chemicals using ducts. It derives from the Greek words "endo"...

, its diseases, and its specific secretions called hormone
Hormone
A hormone is a chemical released by a cell or a gland in one part of the body that sends out messages that affect cells in other parts of the organism. Only a small amount of hormone is required to alter cell metabolism. In essence, it is a chemical messenger that transports a signal from one...

s, the integration of developmental events such as proliferation, growth, and differentiation (including histogenesis
Histogenesis
Histogenesis is the formation of different tissues from undifferentiated cells. These cells are constituents of three primary germ layers, the endoderm, mesoderm, and ectoderm...

 and organogenesis
Organogenesis
In animal development, organogenesis is the process by which the ectoderm, endoderm, and mesoderm develop into the internal organs of the organism. Internal organs initiate development in humans within the 3rd to 8th weeks in utero...

) and the coordination of metabolism
Metabolism
Metabolism is the set of chemical reactions that happen in the cells of living organisms to sustain life. These processes allow organisms to grow and reproduce, maintain their structures, and respond to their environments. Metabolism is usually divided into two categories...

, respiration
Respiration (physiology)
'In physiology, respiration is defined as the transport of oxygen from the outside air to the cells within tissues, and the transport of carbon dioxide in the opposite direction...

, excretion
Excretion
Excretion is the process by which waste products of metabolism and other non-useful materials are eliminated from an organism. This is primarily carried out by the lungs, kidneys and skin. This is in contrast with secretion, where the substance may have specific tasks after leaving the cell...

, movement
Movement
-In society and the arts:* Social movement, a coordinated group action focused on a political or social issue* Political movement, a coordinated group action focused on a political issue* Art movement, a tendency or style in art followed by a group of artists...

, reproduction, and sensory perception depend on chemical cues, substances synthesized and secreted by specialized cells.

Endocrinology is concerned with the study of the biosynthesis, storage, chemistry, and physiological function of hormones and with the cells of the endocrine glands and tissues that secrete them.

The endocrine system consists of several glands, all and in different parts of the body, that secrete hormones directly into the blood rather than into a duct system. Hormones have many different functions and modes of action; one hormone may have several effects on different target organs, and, conversely, one target organ may be affected by more than one hormone.

In the original 1902 definition by Bayliss and Starling (see below), they specified that, to be classified as a hormone, a chemical must be produced by an organ, be released (in small amounts) into the blood, and be transported by the blood to a distant organ to exert its specific function. This definition holds for most "classical" hormones, but there are also paracrine mechanisms (chemical communication between cells within a tissue or organ), autocrine signals (a chemical that acts on the same cell), and intracrine
Intracrine
Intracrine refers to a hormone that acts inside a cell. Steroid hormones act through intracellular receptors and, thus, may be considered to be intracrines. In contrast, peptide or protein hormones, in general, act as endocrines, autocrines, or paracrines by binding to their receptors present on...

 signals (a chemical that acts within the same cell). A neuroendocrine signal is a "classical" hormone that is released into the blood by a neurosecretory neuron (see article on neuroendocrinology
Neuroendocrinology
Neuroendocrinology is the study of the extensive interactions between the nervous system and the endocrine system, including the biological features of the cells that participate, and how they functionally communicate...

).

Hormones act by binding to specific receptors
Receptor (biochemistry)
In biochemistry, a receptor is a molecule found on the surface of a cell, which receives specific chemical signals from neighbouring cells or the wider environment within an organism...

 in the target organ. As Baulieu
Étienne-Émile Baulieu
Étienne-Émile Baulieu is a French biochemist and endocrinologist who is best known for his research in the field of steroid hormones and their role in reproduction and aging.-Biography:...

 notes, a receptor has at least two basic constituents:
  • a recognition site, to which the hormone binds
  • an effector site, which precipitates the modification of cellular function.


Between these is a "transduction mechanism" in which hormone binding induces allosteric modification that, in turn, produces the appropriate response.

Chemical classes of hormones

Griffin
Griffin
The griffin, griffon, or gryphon is a legendary creature with the body of a lion and the head and wings of an eagle...

 and Ojeda
Ojeda
-Municipalities in Spain:*Báscones de Ojeda*La Vid de Ojeda*Micieces de Ojeda*Olmos de Ojeda*Payo de Ojeda*Prádanos de Ojeda-People:*Alonso de Ojeda -Municipalities in Spain:*Báscones de Ojeda*La Vid de Ojeda*Micieces de Ojeda*Olmos de Ojeda*Payo de Ojeda*Prádanos de Ojeda-People:*Alonso de Ojeda...

 identify three different classes of hormone based on their chemical composition:

Amines

Amines, such as norepinephrine
Norepinephrine
Norepinephrine is the US name for noradrenaline , a catecholamine with multiple roles including as a hormone and a neurotransmitter...

, epinephrine
Epinephrine
Epinephrine is a hormone and a neurotransmitter. It increases heart rate, constricts blood vessels, dilates air passages and participates in the fight-or-flight response of the sympathetic nervous system. In chemical terms, adrenaline is one of a group of monoamines called the catecholamines...

, and dopamine
Dopamine
Dopamine is a catecholamine neurotransmitter present in a wide variety of animals, including both vertebrates and invertebrates. In the brain, this substituted phenethylamine functions as a neurotransmitter, activating the five known types of dopamine receptors—D1, D2, D3, D4, and D5—and their...

, are derived from single amino acids, in this case tyrosine. Thyroid
Thyroid
The thyroid gland or simply, the thyroid , in vertebrate anatomy, is one of the largest endocrine glands. The thyroid gland is found in the neck, below the thyroid cartilage...

 hormones such as 3,5,3’-triiodothyronine (T3) and 3,5,3’,5’-tetraiodothyronine (thyroxine, T4) make up a subset of this class because they derive from the combination of two iodinated tyrosine amino acid residues.

Peptide and protein

Peptide hormones and protein hormones consist of three (in the case of thyrotropin-releasing hormone
Thyrotropin-releasing hormone
Thyrotropin-releasing hormone , also called thyrotropin-releasing factor , thyroliberin or protirelin, is a tropic tripeptide hormone that stimulates the release of thyroid-stimulating hormone and prolactin by the anterior pituitary...

) to more than 200 (in the case of follicle-stimulating hormone
Follicle-stimulating hormone
Follicle-stimulating hormone is a hormone found in humans and other animals. It is synthesized and secreted by gonadotrophs of the anterior pituitary gland. FSH regulates the development, growth, pubertal maturation, and reproductive processes of the body. FSH and Luteinizing hormone act...

) amino acid residues and can have molecular weights as large as 30,000. All hormones secreted by the pituitary gland are peptide hormones, as are leptin
Leptin
Leptin is a 16 kDa protein hormone that plays a key role in regulating energy intake and energy expenditure, including appetite and metabolism. It is one of the most important adipose derived hormones...

 from adipocytes, ghrelin
Ghrelin
Ghrelin is a 28 amino acid peptide and hormone that is produced mainly by P/D1 cells lining the fundus of the human stomach and epsilon cells of the pancreas that stimulates hunger. Ghrelin levels increase before meals and decrease after meals. It is considered the counterpart of the hormone...

 from the stomach, and insulin
Insulin
Insulin is a hormone central to regulating carbohydrate and fat metabolism in the body. Insulin causes cells in the liver, muscle, and fat tissue to take up glucose from the blood, storing it as glycogen in the liver and muscle....

 from the pancreas
Pancreas
The pancreas is a gland organ in the digestive and endocrine system of vertebrates. It is both an endocrine gland producing several important hormones, including insulin, glucagon, and somatostatin, as well as a digestive organ, secreting pancreatic juice containing digestive enzymes that assist...

.

Steroid

Steroid hormones are converted from their parent compound, cholesterol
Cholesterol
Cholesterol is a complex isoprenoid. Specifically, it is a waxy steroid of fat that is produced in the liver or intestines. It is used to produce hormones and cell membranes and is transported in the blood plasma of all mammals. It is an essential structural component of mammalian cell membranes...

. Mammalian steroid hormones can be grouped into five groups by the receptors to which they bind: glucocorticoids, mineralocorticoids, androgens, estrogens, and progestagens.

History and key discoveries of endocrinology

The study of endocrinology began in China. The Chinese were isolating sex and pituitary hormones from human urine
Urine
Urine is a typically sterile liquid by-product of the body that is secreted by the kidneys through a process called urination and excreted through the urethra. Cellular metabolism generates numerous by-products, many rich in nitrogen, that require elimination from the bloodstream...

 and using them for medicinal purposes by 200 BCE. They used many complex methods, such as sublimation. Chinese medical texts, some dating no later than 1110, specified a method with the use of gypsum
Gypsum
Gypsum is a very soft sulfate mineral composed of calcium sulfate dihydrate, with the chemical formula CaSO4·2H2O. It is found in alabaster, a decorative stone used in Ancient Egypt. It is the second softest mineral on the Mohs Hardness Scale...

 (containing calcium sulfate
Calcium sulfate
Calcium sulfate is a common laboratory and industrial chemical. In the form of γ-anhydrite , it is used as a desiccant. It is also used as a coagulant in products like tofu. In the natural state, unrefined calcium sulfate is a translucent, crystalline white rock...

) as well as saponin
Saponin
Saponins are a class of chemical compounds, one of many secondary metabolites found in natural sources, with saponins found in particular abundance in various plant species...

 from the beans of Gleditschia sinensis to extract hormones. Eventually, in 1849, when Berthold
Arnold Adolph Berthold
Arnold Adolph Berthold or Arnold Adolf Berthold was a German physiologist and zoologist. He studied medicine in Göttingen in 1819 and wrote his thesis under the direction of Johann Friedrich Blumenbach . Berthold became a private lecturer in 1825 and began to teach physiology at the University of...

 noted that castrated cockerels did not develop combs and wattles or exhibit overtly male behaviour, European endocrinology began. He found that replacement of testes back into the abdominal cavity of the same bird or another castrated bird resulted in normal behavioural and morphological development, and he concluded (erroneously) that the testes secreted a substance that "conditioned" the blood that, in turn, acted on the body of the cockerel. In fact, one of two other things could have been true: that the testes modified or activated a constituent of the blood or that the testes removed an inhibitory factor from the blood. It was not proven that the testes released a substance that engenders male characteristics until it was shown that the extract of testes could replace their function in castrated animals. Pure, crystalline testosterone
Testosterone
Testosterone is a steroid hormone from the androgen group and is found in mammals, reptiles, birds, and other vertebrates. In mammals, testosterone is primarily secreted in the testes of males and the ovaries of females, although small amounts are also secreted by the adrenal glands...

 was isolated in 1938.

Although most of the relevant tissues and endocrine glands had been identified by early anatomists, a more humoral approach to understanding biological function and disease was favoured by the ancient Greek
Ancient Greece
Ancient Greece is a civilization belonging to a period of Greek history that lasted from the Archaic period of the 8th to 6th centuries BC to the end of antiquity. Immediately following this period was the beginning of the Early Middle Ages and the Byzantine era. Included in Ancient Greece is the...

 and Roman
Ancient Rome
Ancient Rome was a thriving civilization that grew on the Italian Peninsula as early as the 8th century BC. Located along the Mediterranean Sea and centered on the city of Rome, it expanded to one of the largest empires in the ancient world....

 thinkers such as Aristotle
Aristotle
Aristotle was a Greek philosopher and polymath, a student of Plato and teacher of Alexander the Great. His writings cover many subjects, including physics, metaphysics, poetry, theater, music, logic, rhetoric, linguistics, politics, government, ethics, biology, and zoology...

, Hippocrates
Hippocrates
Hippocrates of Cos or Hippokrates of Kos was an ancient Greek physician of the Age of Pericles , and is considered one of the most outstanding figures in the history of medicine...

, Lucretius
Lucretius
Titus Lucretius Carus was a Roman poet and philosopher. His only known work is an epic philosophical poem laying out the beliefs of Epicureanism, De rerum natura, translated into English as On the Nature of Things or "On the Nature of the Universe".Virtually no details have come down concerning...

, Celsus
Aulus Cornelius Celsus
Aulus Cornelius Celsus was a Roman encyclopedist, known for his extant medical work, De Medicina, which is believed to be the only surviving section of a much larger encyclopedia. The De Medicina is a primary source on diet, pharmacy, surgery and related fields, and it is one of the best sources...

, and Galen
Galen
Aelius Galenus or Claudius Galenus , better known as Galen of Pergamon , was a prominent Roman physician, surgeon and philosopher...

, according to Freeman et al., and these theories held sway until the advent of germ theory
Germ theory of disease
The germ theory of disease, also called the pathogenic theory of medicine, is a theory that proposes that microorganisms are the cause of many diseases...

, physiology, and organ basis of pathology in the 19th century.

In medieval Persia
History of Iran
The history of Iran has been intertwined with the history of a larger historical region, comprising the area from the Danube River in the west to the Indus River and Jaxartes in the east and from the Caucasus, Caspian Sea, and Aral Sea in the north to the Persian Gulf and the Gulf of Oman and Egypt...

, Avicenna
Avicenna
Abū ʿAlī al-Ḥusayn ibn ʿAbd Allāh ibn Sīnā , commonly known as Ibn Sīnā or by his Latinized name Avicenna, was a Persian polymath, who wrote almost 450 treatises on a wide range of subjects, of which around 240 have survived...

 (980-1037) provided a detailed account on diabetes mellitus
Diabetes mellitus
Diabetes mellitus, often simply referred to as diabetes, is a group of metabolic diseases in which a person has high blood sugar, either because the body does not produce enough insulin, or because cells do not respond to the insulin that is produced...

 in The Canon of Medicine
The Canon of Medicine
The Canon of Medicine is an encyclopedia of Galenic medicine in five books compiled by Ibn Sīnā and completed in 1025. It presents a clear and organized summary of all the medical knowledge of the time...

(c. 1025), "describing the abnormal appetite and the collapse of sexual functions and he documented the sweet taste of diabetic urine." Like Aretaeus of Cappadocia
Aretaeus of Cappadocia
Aretaeus , is one of the most celebrated of the ancient Greek physicians, of whose life, however, few particulars are known. There is some uncertainty regarding both his age and country, but it seems probable that he practised in the 1st century CE, during the reign of Nero or Vespasian...

 before him, Avicenna recognized a primary and secondary diabetes. He also described diabetic gangrene
Gangrene
Gangrene is a serious and potentially life-threatening condition that arises when a considerable mass of body tissue dies . This may occur after an injury or infection, or in people suffering from any chronic health problem affecting blood circulation. The primary cause of gangrene is reduced blood...

, and treated diabetes using a mixture of lupin
Lupin
Lupinus, commonly known as Lupins or lupines , is a genus in the legume family . The genus comprises about 280 species , with major centers of diversity in South and western North America , and the Andes and secondary centers in the Mediterranean region and Africa Lupinus, commonly known as Lupins...

e, trigonella
Trigonella
Trigonella is a genus from the family Fabaceae. The best known member is the herb Fenugreek.-Species:The genus Trigonella currently has 37 recognized species:* Trigonella anguina Delile* Trigonella arabica Delile...

 (fenugreek
Fenugreek
Fenugreek is a plant in the family Fabaceae. Fenugreek is used both as a herb and as a spice . The leaves and sprouts are also eaten as vegetables...

), and zedoary
Zedoary
Zedoary is the name for a perennial herb and member of the genus Curcuma Linn., family Zingiberaceae. The plant is native to India and Indonesia...

 seed, which produces a considerable reduction in the excretion of sugar, a treatment which is still prescribed in modern times. Avicenna
Avicenna
Abū ʿAlī al-Ḥusayn ibn ʿAbd Allāh ibn Sīnā , commonly known as Ibn Sīnā or by his Latinized name Avicenna, was a Persian polymath, who wrote almost 450 treatises on a wide range of subjects, of which around 240 have survived...

 also "described diabetes insipidus very precisely for the first time", though it was later Johann Peter Frank
Johann Peter Frank
Johann Peter Frank was a German physician and hygienist who was a native of Rodalben.He studied medicine at the Universities of Strasbourg and Heidelberg, and earned his medical doctorate in 1766. He was professor at the Universities of Pavia and Göttingen, and for a period of time was personal...

 (1745–1821) who first differentiated between diabetes mellitus and diabetes insipidus.

In the 12th century, Zayn al-Din al-Jurjani, another Muslim physician
Islamic medicine
In the history of medicine, Islamic medicine, Arabic medicine or Arabian medicine refers to medicine developed in the Islamic Golden Age, and written in Arabic, the lingua franca of Islamic civilization....

, provided the first description of Graves' disease
Graves' disease
Graves' disease is an autoimmune disease where the thyroid is overactive, producing an excessive amount of thyroid hormones...

 after noting the association of goitre
Goitre
A goitre or goiter , is a swelling in the thyroid gland, which can lead to a swelling of the neck or larynx...

 and exophthalmos
Exophthalmos
Exophthalmos is a bulging of the eye anteriorly out of the orbit. Exophthalmos can be either bilateral or unilateral . Measurement of the degree of exophthalmos is performed using an exophthalmometer...

 in his Thesaurus of the Shah of Khwarazm, the major medical dictionary of its time. Al-Jurjani also established an association between goitre and palpitation
Palpitation
A palpitation is an abnormality of heartbeat that causes a conscious awareness of its beating, whether it is too slow, too fast, irregular, or at its normal frequency. The word may also refer to this sensation itself...

. The disease was later named after Irish doctor Robert James Graves, who described a case of goiter with exophthalmos
Exophthalmos
Exophthalmos is a bulging of the eye anteriorly out of the orbit. Exophthalmos can be either bilateral or unilateral . Measurement of the degree of exophthalmos is performed using an exophthalmometer...

 in 1835. The German Karl Adolph von Basedow
Karl Adolph von Basedow
Carl Adolph von Basedow was a German physician most famous for reporting the symptoms of what could later be dubbed Graves-Basedow disease, now technically known as exophthalmic goiter.-Biography:...

 also independently reported the same constellation of symptoms in 1840, while earlier reports of the disease were also published by the Italians Giuseppe Flajani and Antonio Giuseppe Testa, in 1802 and 1810 respectively, and by the English physician Caleb Hillier Parry (a friend of Edward Jenner
Edward Jenner
Edward Anthony Jenner was an English scientist who studied his natural surroundings in Berkeley, Gloucestershire...

) in the late 18th century.

In 1902 Bayliss
Bayliss
Bayliss may refer to:places* Bayliss, California, in Glenn Countypeople* Adam Bayliss, film producer* Brendan Bayliss, musician* David Bayliss, footballer* Edward Bayliss, cricketer* Garland E...

 and Starling
Starling
Starlings are small to medium-sized passerine birds in the family Sturnidae. The name "Sturnidae" comes from the Latin word for starling, sturnus. Many Asian species, particularly the larger ones, are called mynas, and many African species are known as glossy starlings because of their iridescent...

 performed an experiment in which they observed that acid instilled into the duodenum
Duodenum
The duodenum is the first section of the small intestine in most higher vertebrates, including mammals, reptiles, and birds. In fish, the divisions of the small intestine are not as clear and the terms anterior intestine or proximal intestine may be used instead of duodenum...

 caused the pancreas
Pancreas
The pancreas is a gland organ in the digestive and endocrine system of vertebrates. It is both an endocrine gland producing several important hormones, including insulin, glucagon, and somatostatin, as well as a digestive organ, secreting pancreatic juice containing digestive enzymes that assist...

 to begin secretion, even after they had removed all nervous connections between the two. The same response could be produced by injecting extract of jejunum mucosa into the jugular vein, showing that some factor in the mucosa was responsible. They named this substance "secretin
Secretin
Secretin is a hormone that controls the secretions into the duodenum, and also separately, water homeostasis throughout the body. It is produced in the S cells of the duodenum in the crypts of Lieberkühn...

" and coined the term hormone for chemicals that act in this way.

Von Mering and Minkowski made the observation in 1889 that removing the pancreas
Pancreas
The pancreas is a gland organ in the digestive and endocrine system of vertebrates. It is both an endocrine gland producing several important hormones, including insulin, glucagon, and somatostatin, as well as a digestive organ, secreting pancreatic juice containing digestive enzymes that assist...

 surgically led to an increase in blood sugar
Blood sugar
The blood sugar concentration or blood glucose level is the amount of glucose present in the blood of a human or animal. Normally in mammals, the body maintains the blood glucose level at a reference range between about 3.6 and 5.8 mM , or 64.8 and 104.4 mg/dL...

, followed by a coma and eventual death—symptoms of diabetes mellitus
Diabetes mellitus
Diabetes mellitus, often simply referred to as diabetes, is a group of metabolic diseases in which a person has high blood sugar, either because the body does not produce enough insulin, or because cells do not respond to the insulin that is produced...

. In 1922, Banting and Best realized that homogenizing the pancreas and injecting the derived extract reversed this condition. The hormone responsible, insulin
Insulin
Insulin is a hormone central to regulating carbohydrate and fat metabolism in the body. Insulin causes cells in the liver, muscle, and fat tissue to take up glucose from the blood, storing it as glycogen in the liver and muscle....

, was not discovered until Frederick Sanger sequenced it in 1953.

Neurohormone
Neurohormone
A neurohormone is any hormone produced and released by neurons.Examples include:*Thyrotropin-releasing hormone *Gonadotropin-releasing hormone *Adrenocorticotropin-releasing hormone*Oxytocin*Antidiuretic hormone *Epinephrine...

s were first identified by Otto Loewi
Otto Loewi
Otto Loewi was a German born pharmacologist whose discovery of acetylcholine helped enhance medical therapy. The discovery earned for him the Nobel Prize in Physiology or Medicine in 1936 which he shared with Sir Henry Dale, whom he met in 1902 when spending some months in Ernest Starling's...

 in 1921. He incubated a frog's heart (innervated with its vagus nerve
Vagus nerve
The vagus nerve , also called pneumogastric nerve or cranial nerve X, is the tenth of twelve paired cranial nerves...

 attached) in a saline bath, and left in the solution for some time. The solution was then used to bathe a non-innervated second heart. If the vagus nerve on the first heart was stimulated, negative inotropic (beat amplitude) and chronotropic
Chronotropic
Chronotropic effects are those that change the heart rate.Chronotropic drugs may change the heart rate by affecting the nerves controlling the heart, or by changing the rhythm produced by the sinoatrial node...

 (beat rate) activity were seen in both hearts. This did not occur in either heart if the vagus nerve was not stimulated. The vagus nerve was adding something to the saline solution. The effect could be blocked using atropine
Atropine
Atropine is a naturally occurring tropane alkaloid extracted from deadly nightshade , Jimson weed , mandrake and other plants of the family Solanaceae. It is a secondary metabolite of these plants and serves as a drug with a wide variety of effects...

, a known inhibitor
Inhibitor
Something that restrains, blocks, or suppresses.Inhibitor or inhibition may refer to:* Corrosion inhibitor, a substance that decreases the rate of metal oxidation...

 to heart
Heart
The heart is a myogenic muscular organ found in all animals with a circulatory system , that is responsible for pumping blood throughout the blood vessels by repeated, rhythmic contractions...

 vagal nerve stimulation. Clearly, something was being secreted by the vagus nerve
Vagus nerve
The vagus nerve , also called pneumogastric nerve or cranial nerve X, is the tenth of twelve paired cranial nerves...

 and affecting the heart. The "vagusstuff" (as Loewi called it) causing the myotropic (muscle enhancing) effects was later identified to be acetylcholine
Acetylcholine
The chemical compound acetylcholine is a neurotransmitter in both the peripheral nervous system and central nervous system in many organisms including humans...

 and norepinephrine
Norepinephrine
Norepinephrine is the US name for noradrenaline , a catecholamine with multiple roles including as a hormone and a neurotransmitter...

. Loewi won the Nobel Prize for his discovery.

Recent work in endocrinology focuses on the molecular mechanisms responsible for triggering the effects of hormone
Hormone
A hormone is a chemical released by a cell or a gland in one part of the body that sends out messages that affect cells in other parts of the organism. Only a small amount of hormone is required to alter cell metabolism. In essence, it is a chemical messenger that transports a signal from one...

s. The first example of such work being done was in 1962 by Earl Sutherland
Earl Wilbur Sutherland Jr.
Earl Wilbur Sutherland Jr. was an American pharmacologist and biochemist. Sutherland was born in Burlingame, Kansas...

. Sutherland investigated whether hormones enter cells to evoke action, or stayed outside of cells. He studied norepinephrine
Norepinephrine
Norepinephrine is the US name for noradrenaline , a catecholamine with multiple roles including as a hormone and a neurotransmitter...

, which acts on the liver to convert glycogen
Glycogen
Glycogen is a molecule that serves as the secondary long-term energy storage in animal and fungal cells, with the primary energy stores being held in adipose tissue...

 into glucose
Glucose
Glucose is a simple sugar and an important carbohydrate in biology. Cells use it as the primary source of energy and a metabolic intermediate...

 via the activation of the phosphorylase
Phosphorylase
Phosphorylases are enzymes that catalyze the addition of a phosphate group from an inorganic phosphate to an acceptor.They include allosteric enzymes that catalyze the production of glucose-1-phosphate from a glucan such as glycogen, starch or maltodextrin. Phosphorylase is also a common name used...

 enzyme. He homogenized the liver into a membrane fraction and soluble fraction (phosphorylase is soluble), added norepinephrine to the membrane fraction, extracted its soluble products, and added them to the first soluble fraction. Phosphorylase activated, indicating that norepinephrine's target receptor was on the cell membrane, not located intracellularly. He later identified the compound as cyclic AMP (cAMP
Cyclic adenosine monophosphate
Cyclic adenosine monophosphate is a second messenger important in many biological processes...

) and with his discovery created the concept of second-messenger-mediated pathways. He, like Loewi, won the Nobel Prize for his groundbreaking work in endocrinology.

Endocrinology as a profession

Although every organ system secretes and responds to hormones (including the brain
Human brain
The human brain has the same general structure as the brains of other mammals, but is over three times larger than the brain of a typical mammal with an equivalent body size. Estimates for the number of neurons in the human brain range from 80 to 120 billion...

, lungs, heart
Human heart
The human heart is a muscular organ that provides a continuous blood circulation through the cardiac cycle and is one of the most vital organs in the human body...

, intestine
Intestine
In human anatomy, the intestine is the segment of the alimentary canal extending from the pyloric sphincter of the stomach to the anus and, in humans and other mammals, consists of two segments, the small intestine and the large intestine...

, skin
Human skin
The human skin is the outer covering of the body. In humans, it is the largest organ of the integumentary system. The skin has multiple layers of ectodermal tissue and guards the underlying muscles, bones, ligaments and internal organs. Human skin is similar to that of most other mammals,...

, and the kidney
Kidney
The kidneys, organs with several functions, serve essential regulatory roles in most animals, including vertebrates and some invertebrates. They are essential in the urinary system and also serve homeostatic functions such as the regulation of electrolytes, maintenance of acid–base balance, and...

), the clinical specialty of endocrinology focuses primarily on the endocrine organs, meaning the organs whose primary function is hormone secretion. These organs include the pituitary, thyroid
Thyroid
The thyroid gland or simply, the thyroid , in vertebrate anatomy, is one of the largest endocrine glands. The thyroid gland is found in the neck, below the thyroid cartilage...

, adrenals, ovaries
Ovary
The ovary is an ovum-producing reproductive organ, often found in pairs as part of the vertebrate female reproductive system. Ovaries in anatomically female individuals are analogous to testes in anatomically male individuals, in that they are both gonads and endocrine glands.-Human anatomy:Ovaries...

, testes, and pancreas
Pancreas
The pancreas is a gland organ in the digestive and endocrine system of vertebrates. It is both an endocrine gland producing several important hormones, including insulin, glucagon, and somatostatin, as well as a digestive organ, secreting pancreatic juice containing digestive enzymes that assist...

.

An endocrinologist is a doctor
Physician
A physician is a health care provider who practices the profession of medicine, which is concerned with promoting, maintaining or restoring human health through the study, diagnosis, and treatment of disease, injury and other physical and mental impairments...

 who specializes in treating disorders of the endocrine system, such as diabetes, hyperthyroidism
Hyperthyroidism
Hyperthyroidism is the term for overactive tissue within the thyroid gland causing an overproduction of thyroid hormones . Hyperthyroidism is thus a cause of thyrotoxicosis, the clinical condition of increased thyroid hormones in the blood. Hyperthyroidism and thyrotoxicosis are not synonymous...

, and many others (see list of diseases below).

Work

The medical specialty of endocrinology involves the diagnostic evaluation of a wide variety of symptoms and variations and the long-term management of disorders of deficiency or excess of one or more hormones.

The diagnosis and treatment of endocrine diseases are guided by laboratory
Laboratory
A laboratory is a facility that provides controlled conditions in which scientific research, experiments, and measurement may be performed. The title of laboratory is also used for certain other facilities where the processes or equipment used are similar to those in scientific laboratories...

 tests to a greater extent than for most specialties. Many diseases are investigated through excitation/stimulation or inhibition/suppression testing. This might involve injection with a stimulating agent to test the function of an endocrine organ. Blood is then sampled to assess the changes of the relevant hormones or metabolites. An endocrinologist needs extensive knowledge of clinical chemistry and biochemistry
Biochemistry
Biochemistry, sometimes called biological chemistry, is the study of chemical processes in living organisms, including, but not limited to, living matter. Biochemistry governs all living organisms and living processes...

 to understand the uses and limitations of the investigations.

A second important aspect of the practice of endocrinology is distinguishing human variation from disease. Atypical patterns of physical development and abnormal test results must be assessed as indicative of disease or not. Diagnostic imaging of endocrine organs may reveal incidental findings called incidentaloma
Incidentaloma
In medicine, an incidentaloma is a tumor found by coincidence without clinical symptoms or suspicion. It is a common problem: up to 7% of all patients over 60 may harbor a benign growth, often of the adrenal gland, which is detected when diagnostic imaging is used for the analysis of unrelated...

s, which may or may not represent disease.

Endocrinology involves caring for the person biology as well as the nucleus the enzymes as well as the disease. Most endocrine disorders are chronic diseases that need life-long care. Some of the most common endocrine diseases include diabetes mellitus, hypothyroidism
Hypothyroidism
Hypothyroidism is a condition in which the thyroid gland does not make enough thyroid hormone.Iodine deficiency is the most common cause of hypothyroidism worldwide but it can be caused by other causes such as several conditions of the thyroid gland or, less commonly, the pituitary gland or...

 and the metabolic syndrome. Care of diabetes, obesity and other chronic diseases necessitates understanding the patient at the personal and social level as well as the molecular, and the physician–patient relationship can be an important therapeutic process.

Apart from treating patients, many endocrinologists are involved in clinical science and medical research, teaching, and hospital management.

Training

There are roughly 4,000 endocrinologists in the United States. Endocrinologists are specialists of internal medicine
Internal medicine
Internal medicine is the medical specialty dealing with the prevention, diagnosis, and treatment of adult diseases. Physicians specializing in internal medicine are called internists. They are especially skilled in the management of patients who have undifferentiated or multi-system disease processes...

 or pediatrics
Pediatrics
Pediatrics or paediatrics is the branch of medicine that deals with the medical care of infants, children, and adolescents. A medical practitioner who specializes in this area is known as a pediatrician or paediatrician...

. Reproductive endocrinologists deal primarily with problems of fertility
Fertility
Fertility is the natural capability of producing offsprings. As a measure, "fertility rate" is the number of children born per couple, person or population. Fertility differs from fecundity, which is defined as the potential for reproduction...

 and menstrual function—often training first in obstetrics. Most qualify as an internist, pediatrician, or gynecologist for a few years before specializing, depending on the local training system. In the U.S. and Canada, training for board certification in internal medicine, pediatrics
Pediatrics
Pediatrics or paediatrics is the branch of medicine that deals with the medical care of infants, children, and adolescents. A medical practitioner who specializes in this area is known as a pediatrician or paediatrician...

, or gynecology after medical school is called residency. Further formal training to subspecialize in adult, pediatric
Pediatric endocrinology
Pediatric endocrinology is a medical subspecialty dealing with variations of physical growth and sexual development in childhood, as well as diabetes and other disorders of the endocrine glands....

, or reproductive endocrinology is called a fellowship. Typical training for a North American endocrinologist involves 4 years of college, 4 years of medical school, 3 years of residency, and 2 years of fellowship. Adult endocrinologists are board certified by the American Board of Internal Medicine
American Board of Internal Medicine
The American Board of Internal Medicine is a non-profit, independent physician evaluation organization committed to continuously improving the profession for the public good by certifying physicians who practice internal medicine and its sub-specialties...

 (ABIM) in Endocrinology, Diabetes and Metabolism.

Professional organizations

In North America the principal professional organizations of endocrinologists include The Endocrine Society, the American Association of Clinical Endocrinologists, the American Diabetes Association, the Lawson Wilkins Pediatric Endocrine Society, and the American Thyroid Association.

In the United Kingdom, the Society for Endocrinology and the British Society for Paediatric Endocrinology and Diabetes are the main professional organisations. The European Society for Paediatric Endocrinology is the largest international professional association dedicated solely to paediatric endocrinology. There are numerous similar associations around the world.

Patient education

Because endocrinology encompasses so many conditions and diseases, there are many organizations that provide education to patients and the public. The Hormone Foundation
The Hormone Foundation
The Hormone Foundation, established in 1997 by The Endocrine Society as its public education affiliate, serves as a resource for physicians, patients, and the public by promoting the prevention, treatment and cure of hormone-related conditions through outreach and education.The Hormone Foundation...

 is the public education affiliate of The Endocrine Society
The Endocrine Society
The Endocrine Society is a professional, international medical organization in the field of endocrinology and metabolism, founded in 1916 as The Association for the Study of Internal Secretions. The official name of the organization was changed to The Endocrine Society on January 1, 1952. It is a...

 and provides information on all endocrine-related conditions. Other educational organizations that focus on one or more endocrine-related conditions include the American Diabetes Association
American Diabetes Association
The American Diabetes Association is a United States-based association working to fight the consequences of diabetes, and to help those affected by diabetes...

, National Osteoporosis Foundation, Human Growth Foundation, American Menopause Foundation, Inc., and Thyroid Foundation of America.

Diseases

See main article at Endocrine diseases

A disease due to a disorder of the endocrine system is often called a "hormone imbalance", but is technically known as an endocrinopathy or endocrinosis. Such disease can be treated by reducing the hormone which has become imbalanced.

In popular culture

  • Lisa Cuddy
    Lisa Cuddy
    Dr. Lisa Cuddy, M.D., is a fictional character on the Fox medical drama House. She is portrayed by Lisa Edelstein. Cuddy was the Dean of Medicine and hospital administrator of the fictional Princeton-Plainsboro Teaching Hospital in New Jersey. She also becomes House's love interest through the...

    , a character on the television show House M.D.
  • Elliot Reid
    Elliot Reid
    Dr. Elliot Reid is a fictional character played by Sarah Chalke in the American comedy-drama Scrubs. She has appeared in every episode during the first eight seasons except two Season 8 episodes, "My Last Words" and "My Lawyer's in Love"....

    , a character who becomes an expert in the field in the Scrubs
    Scrubs (TV series)
    Scrubs is an American medical comedy-drama television series created in 2001 by Bill Lawrence and produced by ABC Studios. The show follows the lives of several employees of the fictional Sacred Heart, a teaching hospital. It features fast-paced screenplay, slapstick, and surreal vignettes...

    episode "My Way Home
    My Way Home
    "My Way Home" is the 7th episode of season five and the 100th episode of the American comedy-drama Scrubs. It originally aired on January 24, 2006 on NBC....

    "
  • Naomi Bennett
    Naomi Bennett
    Naomi Bennett is a fictional character on the Grey's Anatomy spin-off Private Practice. She was played by Merrin Dungey in the backdoor pilot episode "The Other Side of This Life", but was replaced by Audra McDonald prior to the show's first season. Naomi is a obstetrician/gynecologist and founding...

    , a character on the television show Private Practice who did her residency in Obstetrics
    Obstetrics
    Obstetrics is the medical specialty dealing with the care of all women's reproductive tracts and their children during pregnancy , childbirth and the postnatal period...

     and Gynecology and her fellowship in Reproductive endocrinology and infertility
    Reproductive endocrinology and infertility
    Reproductive endocrinology and infertility is a surgical subspecialty of obstetrics and gynecology that trains physicians in reproductive medicine addressing hormonal functioning as it pertains to reproduction as well as the issue of infertility...


See also

  • Pediatric endocrinology
    Pediatric endocrinology
    Pediatric endocrinology is a medical subspecialty dealing with variations of physical growth and sexual development in childhood, as well as diabetes and other disorders of the endocrine glands....

  • Neuroendocrinology
    Neuroendocrinology
    Neuroendocrinology is the study of the extensive interactions between the nervous system and the endocrine system, including the biological features of the cells that participate, and how they functionally communicate...

  • Reproductive endocrinology
  • Hormone
    Hormone
    A hormone is a chemical released by a cell or a gland in one part of the body that sends out messages that affect cells in other parts of the organism. Only a small amount of hormone is required to alter cell metabolism. In essence, it is a chemical messenger that transports a signal from one...

  • Endocrine disease
    Endocrine disease
    Endocrine diseases are disorders of the endocrine system. The branch of medicine associated with endocrine disorders is known as endocrinology.-Types of endocrine disease:Broadly speaking, endocrine disorders may be subdivided into three groups:...


External links


Societies and associations

The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
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