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67-447: The endocrine system consists of several glands , all in different parts of the body, that secrete hormones directly into the blood rather than into a duct system. Therefore, endocrine glands are regarded as ductless glands. 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. Endocrinology

134-408: A correlation between pituitary gland volume and Social Anxiety subscale scores was identified which provided a basis for exploring mediation. Again controlling for age, sex, and BMI, DHEA and DHEA-S have been found to be predictive of larger pituitary gland volume, which was also associated with increased ratings of social anxiety. This research provides evidence that pituitary gland volume mediates

201-417: A different method of secretion. Endocrine glands are ductless and secrete their products, hormones , directly into interstitial spaces to be taken up into the bloodstream. Exocrine glands secrete their products through a duct into a body cavity or outer surface. Glands are mostly composed of epithelial tissue , and typically have a supporting framework of connective tissue, and a capsule. Every gland

268-503: 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 , or gynecology after medical school is called residency. Further formal training to subspecialize in adult, pediatric , 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. In

335-474: A gland. The diseased gland has abnormal formation or development of glandular tissue which is sometimes tumorous . Pituitary The pituitary gland or hypophysis is an endocrine gland in vertebrates . In humans , the pituitary gland is located at the base of the brain , protruding off the bottom of the hypothalamus . The human pituitary gland is oval shaped , about 1 cm in diameter, 0.5–1 gram (0.018–0.035 oz) in weight on average, and about

402-429: 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 to understand

469-443: A hormone, or problems with receiving the hormone. Because endocrinology encompasses so many conditions and diseases, there are many organizations that provide education to patients and the public. The Hormone Foundation is the public education affiliate of The Endocrine Society and provides information on all endocrine-related conditions. Other educational organizations that focus on one or more endocrine-related conditions include

536-490: A known inhibitor to heart vagal nerve stimulation. Clearly, something was being secreted by the vagus nerve and affecting the heart. The "vagusstuff" (as Loewi called it) causing the myotropic (muscle enhancing) effects was later identified to be acetylcholine and norepinephrine . Loewi won the Nobel Prize for his discovery. Recent work in endocrinology focuses on the molecular mechanisms responsible for triggering

603-611: A less modified type of epithelial cell. Glands are classified according to their shape. Glands are divided based on their function into two groups: Endocrine glands secrete substances that circulate through the bloodstream. The glands secrete their products through basal lamina into the bloodstream. Basal lamina typically can be seen as a layer around the glands to which more than a million tiny blood vessels are attached. These glands often secrete hormones which play an important role in maintaining homeostasis . The pineal gland , thymus gland , pituitary gland , thyroid gland , and

670-460: 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 (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 ,

737-483: A subset of this class because they derive from the combination of two iodinated tyrosine amino acid residues. Peptide hormones and protein hormones consist of three (in the case of thyrotropin-releasing hormone ) to more than 200 (in the case of follicle-stimulating hormone ) amino acid residues and can have a molecular mass as large as 31,000 grams per mole. All hormones secreted by the pituitary gland are peptide hormones, as are leptin from adipocytes, ghrelin from

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804-403: A very large structure is finally formed by repeated growth and sub-division. As a rule, the branches do not unite with one another. One exception to this rule is the liver ; this occurs when a reticulated compound gland is produced. In compound glands the more typical or secretory epithelium is found forming the terminal portion of each branch, and the uniting portions form ducts and are lined with

871-460: Is a physician who specializes in treating disorders of the endocrine system, such as diabetes , hyperthyroidism , and many others (see list of diseases ). 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 tests to

938-489: Is a "classical" hormone that is released into the blood by a neurosecretory neuron (see article on neuroendocrinology ). Griffin and Ojeda identify three different classes of hormones based on their chemical composition: Amines, such as norepinephrine , epinephrine , and dopamine ( catecholamines ), are derived from single amino acids , in this case tyrosine. Thyroid hormones such as 3,5,3'-triiodothyronine (T3) and 3,5,3',5'-tetraiodothyronine (thyroxine, T4) make up

1005-629: 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). It regulates hydroelectrolytic stability (by secreting ADH ), uterine contraction during labor and human attachment (by secreting oxytocin ). The anterior pituitary synthesizes and secretes hormones. All releasing hormones (-RH) referred to can also be referred to as releasing factors (-RF). Somatotropes : Corticotropes : Thyrotropes : Gonadotropes : Lactotropes : These hormones are released from

1072-423: Is formed by an ingrowth from an epithelial surface. This ingrowth may in the beginning possess a tubular structure, but in other instances glands may start as a solid column of cells which subsequently becomes tubulated. As growth proceeds, the column of cells may split or give off offshoots, in which case a compound gland is formed. In many glands, the number of branches is limited, in others (salivary, pancreas)

1139-437: Is important for mediating the stress response, via the hypothalamic–pituitary–adrenal axis (HPA axis). Critically, pituitary gland growth during adolescence can be altered by early life stress such as childhood maltreatment or maternal dysphoric behavior. It has been demonstrated that, after controlling for age, sex, and BMI, larger quantities of DHEA and DHEA-S tended to be linked to larger pituitary volume. Additionally,

1206-415: Is no pituitary stalk. Rathke's pouch remains open to the outside, close to the nasal openings. Closely associated with the pouch are three distinct clusters of glandular tissue, corresponding to the intermediate lobe, and the rostral and proximal portions of the anterior pituitary. These various parts are separated by meningial membranes, suggesting that the pituitary of other vertebrates may have formed from

1273-408: Is one type of cell for each major hormone formed in anterior pituitary . With special stains attached to high-affinity antibodies that bind with distinctive hormone, at least 5 types of cells can be differentiated. The posterior pituitary consists of the posterior lobe and the pituitary stalk (infundibulum) that connects it to the hypothalamus. It develops as an extension of the hypothalamus, from

1340-402: Is present in many animal species, particularly in rodents, mice, and rats, which have been used extensively to study pituitary development and function. In all animals, the fleshy, glandular anterior pituitary is distinct from the neural composition of the posterior pituitary, which is an extension of the hypothalamus . The height of the pituitary gland ranges from 5.3 to 7.0 mm. The volume of

1407-424: 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 ) and with his discovery created the concept of second-messenger-mediated pathways. He, like Loewi, won

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1474-430: Is still used as official synonym beside hypophysis in the official Latin nomenclature Terminologia Anatomica . In the seventeenth century the supposed function of the pituitary gland to produce nasal mucus was debunked. The expression glandula pituitaria and its English equivalent pituitary gland can only be justified from a historical point of view. The inclusion of this synonym is merely justified by noting that

1541-538: Is the largest international professional association dedicated solely to paediatric endocrinology. There are numerous similar associations around the world. The earliest study of endocrinology began in China. The Chinese were isolating sex and pituitary hormones from human urine and using them for medicinal purposes by 200 BC. They used many complex methods, such as sublimation of steroid hormones. Another method specified by Chinese texts—the earliest dating to 1110—specified

1608-408: Is the study of the endocrine system in the human body . This is a system of glands which secrete hormones. Hormones are chemicals that affect the actions of different organ systems in the body. Examples include thyroid hormone , growth hormone , and insulin . The endocrine system involves a number of feedback mechanisms, so that often one hormone (such as thyroid stimulating hormone ) will control

1675-858: The American Diabetes Association , Human Growth Foundation , American Menopause Foundation, Inc., and American Thyroid Association. 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 Europe,

1742-400: The anterior pituitary ), the intermediate lobe located between the anterior and posterior pituitary is important to many animals. For instance, in fish, it is believed to control physiological color 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

1809-411: The pancreas 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 " and coined the term hormone for chemicals that act in this way. Joseph von Mering and Oskar Minkowski made

1876-455: The sphenoid bone , in the center of the middle cranial fossa . It sits in a protective bony enclosure called the sella turcica , covered by the dural fold diaphragma sellae . The pituitary gland is composed of the anterior pituitary , the posterior pituitary , and an intermediate lobe that joins them. The intermediate lobe is avascular and almost absent in humans. In many animals, these three lobes are distinct. The intermediate lobe

1943-691: The European Society of Endocrinology (ESE) and the European Society for Paediatric Endocrinology (ESPE) are the main organisations representing professionals in the fields of adult and paediatric endocrinology, respectively. 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

2010-541: 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 ) in the late 18th century. Thomas Addison was first to describe Addison's disease in 1849. In 1902 William Bayliss and Ernest Starling performed an experiment in which they observed that acid instilled into the duodenum caused

2077-407: The Nobel Prize for his groundbreaking work in endocrinology. Glands A gland is a cell or an organ in an animal's body that produces and secretes different substances that the organism needs, either into the bloodstream or into a body cavity or outer surface. A gland may also function to remove unwanted substances such as urine from the body. There are two types of gland each with

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2144-653: The US, adult endocrinologists are board certified by the American Board of Internal Medicine (ABIM) or the American Osteopathic Board of Internal Medicine (AOBIM) in Endocrinology, Diabetes and Metabolism. Endocrinology also involves the study of the diseases of the endocrine system. These diseases may relate to too little or too much secretion of a hormone, too little or too much action of

2211-410: The action or release of another secondary hormone (such as thyroid hormone ). If there is too much of the secondary hormone, it may provide negative feedback to the primary hormone, maintaining homeostasis . 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

2278-427: The advent of germ theory , physiology, and organ basis of pathology in the 19th century. In 1849, Arnold Berthold noted that castrated cockerels did not develop combs and wattles or exhibit overtly male behaviour. 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

2345-464: The anterior pituitary under the influence of the hypothalamus . Hypothalamic hormones are secreted to the anterior lobe by way of a special capillary system, called the hypothalamic-hypophysial portal system . There is also a non-endocrine cell population called folliculostellate cells . The posterior pituitary stores and secretes (but does not synthesize) the following important endocrine hormones: Magnocellular neurons : Hormones secreted from

2412-409: The anterior pituitary, but in amphibians , reptiles , and birds , it becomes increasingly well developed. The intermediate lobe is, in general, not well developed in any species and is entirely absent in birds. The structure of the pituitary in fish, apart from the lungfish, is generally different from that in other animals. In general, the intermediate lobe tends to be well developed, and may equal

2479-410: 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 signals (a chemical that acts within the same cell). A neuroendocrine signal

2546-410: The body. This dual-origin structure and function are what make the pituitary gland a unique and critical component of the endocrine system, acting as a bridge between the nervous and endocrine systems. Some of the diseases involving the pituitary gland are: All of the functions of the pituitary gland can be adversely affected by an over- or under-production of associated hormones. The pituitary gland

2613-412: The boundary between the two is often not clearly marked. In elasmobranchs , there is an additional, ventral lobe beneath the anterior pituitary proper. The arrangement in lampreys , which are among the most primitive of all fish, may indicate how the pituitary originally evolved in ancestral vertebrates. Here, the posterior pituitary is a simple flat sheet of tissue at the base of the brain, and there

2680-475: The characteristic fused ring structure of true steroids. Although every organ system secretes and responds to hormones (including the brain , lungs , heart , intestine , skin , and the kidneys ), 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 , adrenals , ovaries , testes , and pancreas . An endocrinologist

2747-565: The developing brain. The upper part of the pouch eventually constricts and detaches from the oral cavity. Cells in Rathke's pouch differentiate to form three parts of the adenohypophysis: the pars distalis, pars intermedia, and pars tuberalis. Formation of the Posterior Pituitary (4th to 8th week): The infundibulum from the diencephalon elongates downward, forming a stalk that connects with Rathke’s pouch. This stalk will develop into

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2814-426: The effects of hormones . The first example of such work being done was in 1962 by Earl Sutherland . Sutherland investigated whether hormones enter cells to evoke action, or stayed outside of cells. He studied norepinephrine , which acts on the liver to convert glycogen into glucose via the activation of the phosphorylase enzyme. He homogenized the liver into a membrane fraction and soluble fraction (phosphorylase

2881-430: The extract of testes could replace their function in castrated animals. Pure, crystalline testosterone was isolated in 1935. Graves' disease was named after Irish doctor Robert James Graves , who described a case of goiter with exophthalmos in 1835. The German Karl Adolph von Basedow also independently reported the same constellation of symptoms in 1840, while earlier reports of the disease were also published by

2948-429: The floor of the third ventricle . The posterior pituitary hormones are synthesized by cell bodies in the hypothalamus . The magnocellular neurosecretory cells , of the supraoptic and paraventricular nuclei located in the hypothalamus, project axons down the infundibulum to terminals in the posterior pituitary. This simple arrangement differs sharply from that of the adjacent anterior pituitary, which does not develop from

3015-415: The fusion of a pair of separate, but associated, glands. Most armadillos also possess a neural secretory gland very similar in form to the posterior pituitary, but located in the tail and associated with the spinal cord . This may have a function in osmoregulation . There is a structure analogous to the pituitary in the octopus brain. Although rudimentary in humans (and often considered part of

3082-423: The hypothalamic capillaries leading to infundibular blood vessels, which in turn lead to a second capillary bed in the anterior pituitary. This vascular relationship constitutes the hypophyseal portal system . Diffusing out of the second capillary bed, the hypothalamic releasing hormones then bind to anterior pituitary endocrine cells, upregulating or downregulating their release of hormones. The anterior lobe of

3149-404: The hypothalamus and releases them into the bloodstream. 4. Final Structural Differentiation The pituitary gland achieves its final form, including the complete separation of anterior and posterior lobes, by the end of the first trimester The gland remains connected to the hypothalamus by the pituitary stalk, allowing it to integrate signals from the brain and regulate various endocrine functions in

3216-422: The hypothalamus. Hormones secreted from the pituitary gland help to control growth , blood pressure , energy management, all functions of the sex organs , thyroid gland , metabolism , as well as some aspects of pregnancy , childbirth , breastfeeding , water/salt concentration at the kidneys , temperature regulation, and pain relief. In humans, the pituitary gland rests upon the hypophyseal fossa of

3283-582: The hypothalamus. The release of pituitary hormones by both the anterior and posterior lobes is under the control of the hypothalamus , albeit in different ways. The anterior pituitary regulates several physiological processes by secreting hormones. This includes stress (by secreting ACTH ), growth (by secreting GH ), reproduction (by secreting FSH and LH ), metabolism rate (by secreting TSH ) and lactation (by secreting prolactin ). The intermediate lobe synthesizes and secretes melanocyte-stimulating hormone . The posterior pituitary (or neurohypophysis)

3350-423: The link between higher DHEA(S) levels (associated with relatively early adrenarche) and traits associated with social anxiety. Children who experience early adrenarcheal development tend to have larger pituitary gland volume compared to children with later adrenarcheal development. The Greek physician Galen referred to the pituitary gland by only using the ( Ancient Greek ) name ἀδήν , gland . He described

3417-667: The main term hypophysis is a much less popular term. Note: hypophysial (or hypophyseal ) means "related to the hypophysis (pituitary gland)". The anatomist Samuel Thomas von Sömmerring coined the name hypophysis . This name consists of ὑπό ('under') and φύειν ('to grow'). In later Greek ὑπόφυσις is used differently by Greek physicians as outgrowth . Sömmering also used the equivalent expression appendix cerebri , with appendix as appendage . In various languages, Hirnanhang in German and hersenaanhangsel in Dutch ,

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3484-438: The observation in 1889 that removing the pancreas surgically led to an increase in blood sugar , followed by a coma and eventual death—symptoms of diabetes mellitus . In 1922, Banting and Best realized that homogenizing the pancreas and injecting the derived extract reversed this condition. Neurohormones were first identified by Otto Loewi in 1921. He incubated a frog's heart (innervated with its vagus nerve attached) in

3551-555: The pars nervosa, or posterior pituitary. Specialized cells from the hypothalamus, known as pituicytes, migrate to the posterior pituitary, where they help store and release hormones such as oxytocin and vasopressin. 3. Hormone Production and Functional Maturity By around the 12th to 16th week of gestation, the anterior pituitary begins producing hormones like growth hormone (GH), adrenocorticotropic hormone (ACTH), and others essential for fetal development. The posterior pituitary functions primarily in storage, as it stores hormones produced by

3618-887: The person as well as the disease. Most endocrine disorders are chronic diseases that need lifelong care. Some of the most common endocrine diseases include diabetes mellitus, hypothyroidism 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 . Endocrinologists are specialists of internal medicine or pediatrics . Reproductive endocrinologists deal primarily with problems of fertility and menstrual function—often training first in obstetrics. Most qualify as an internist , pediatrician , or gynecologist for

3685-561: The pituitary can be divided into the pars tuberalis (pars infundibularis) and pars distalis (pars glandularis) that constitutes ~80% of the gland. The pars intermedia (the intermediate lobe) lies between the pars distalis and the pars tuberalis, and is rudimentary in the human, although in other species it is more developed. It develops from a depression in the dorsal wall of the pharynx (stomal part) known as Rathke's pouch. The anterior pituitary contains several different types of cells that synthesize and secrete hormones. Usually there

3752-408: The pituitary gland as part of a series of secretory organs for the excretion of nasal mucus . Anatomist Andreas Vesalius translated ἀδήν with glans, in quam pituita destillat , "gland in which slime ( pituita ) drips". Besides this 'descriptive' name, Vesalius used glandula pituitaria , from which the English name pituitary gland is ultimately derived. The expression glandula pituitaria

3819-450: The pituitary gland help control the following body processes: The development of the pituitary gland, or hypophysis, is a complex process that occurs early in embryonic life and involves contributions from two distinct embryonic tissues. Here’s a detailed explanation: 1.Embryological Origin The pituitary gland develops from two embryonic tissues: Rathke's pouch: An ectodermal outpocketing from

3886-490: The pituitary gland ranges from 200 to 440 mm . Its most common shape, found in 46% of people is flat, it is convex in 31.2% and concave in 22.8%. The anterior pituitary lobe (adenohypophysis) arises from an evagination of the oral ectoderm ( Rathke's pouch ). This contrasts with the posterior pituitary , which originates from neuroectoderm . Endocrine cells of the anterior pituitary are controlled by regulatory hormones released by parvocellular neurosecretory cells in

3953-405: The remainder of the anterior pituitary in size. The posterior lobe typically forms a sheet of tissue at the base of the pituitary stalk, and in most cases sends irregular finger-like projection into the tissue of the anterior pituitary, which lies directly beneath it. The anterior pituitary is typically divided into two regions, a more anterior rostral portion and a posterior proximal portion, but

4020-511: The roof of the primitive oral cavity, or stomodeum, which gives rise to the anterior pituitary (adenohypophysis). Infundibulum: A downward extension from the neuroectoderm of the diencephalon in the brain, which forms the posterior pituitary (neurohypophysis). 2. Developmental Stages Formation of Rathke's pouch (4th week of gestation): During the 4th week, an invagination of the oral ectoderm occurs, creating Rathke's pouch. Differentiation and Migration (5th to 6th week): Rathke's pouch grows towards

4087-448: The size of a kidney bean . There are two main lobes of the pituitary, an anterior lobe , and a posterior lobe joined and separated by a small intermediate lobe . The anterior lobe (adenohypophysis) is the glandular part that produces and secretes several hormones . The posterior lobe (neurohypophysis) secretes neurohypophysial hormones produced in the hypothalamus . Both lobes have different origins and they are both controlled by

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4154-419: The stomach, and insulin from the pancreas . Steroid hormones are converted from their parent compound, cholesterol . Mammalian steroid hormones can be grouped into five groups by the receptors to which they bind: glucocorticoids , mineralocorticoids , androgens , estrogens , and progestogens . Some forms of vitamin D , such as calcitriol , are steroid-like and bind to homologous receptors, but lack

4221-420: The terms are derived from appendix cerebri . The pituitary gland is found in all vertebrates, but its structure varies among different groups. The division of the pituitary described above is typical of mammals , and is also true, to varying degrees, of all tetrapods . However, only in mammals does the posterior pituitary have a compact shape. In lungfish , it is a relatively flat sheet of tissue lying above

4288-409: 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

4355-408: The two adrenal glands are all endocrine glands. Exocrine glands secrete their products through a duct onto an outer or inner surface of the body, such as the skin or the gastrointestinal tract . Secretion is directly onto the apical surface. The glands in this group can be divided into three groups: Exocrine glands can further be categorized by their product: Adenosis is any disease of

4422-530: The use of saponin (from the beans of Gleditsia sinensis ) to extract hormones, but gypsum (containing calcium sulfate ) was also known to have been used. 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 and Roman thinkers such as Aristotle , Hippocrates , Lucretius , Celsus , and Galen , according to Freeman et al., and these theories held sway until

4489-447: 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 incidentalomas , which may or may not represent disease. Endocrinology involves caring for

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