medical_specialty syndrome of inappropriate antidiuretic hormone secretion
The posterior pituitary ( or neurohypophysis ) is the posterior lobe of the pituitary gland which is part of the endocrine system . The posterior pituitary is not glandular as is the anterior pituitary . Instead , it is largely a collection of axonal projections from the hypothalamus that terminate behind the anterior pituitary which serves as a site for the secretion of neurohypophysial hormones ( oxytocin and vasopressin ) directly into the blood . The hypothalamic  neurohypophyseal system is composed of the hypothalamus ( the paraventricular nucleus and supraoptic nucleus ), posterior pituitary , and these axonal projections . The endocrine system is the collection of glands of an organism that secrete hormones directly into the circulatory system to be carried towards distant target organs . The phenomenon of biochemical processes ' serving to regulate distant tissues by means of secretions directly into the circulatory system is called endocrine signaling . The major endocrine glands include the pineal gland , pituitary gland , pancreas , ovaries , testes , thyroid gland , parathyroid gland , and adrenal glands . The endocrine system is in contrast to the exocrine system , which secretes its hormones to the outside of the body using ducts . The endocrine system is an information signal system like the nervous system , yet its effects and mechanism are classifiably different . The endocrine system ' s effects are slow to initiate , and prolonged in their response , lasting from a few hours up to weeks . The nervous system sends information very quickly , and responses are generally short lived . In vertebrates , the hypothalamus is the neural control center for all endocrine systems . The field of study dealing with the endocrine system and its disorders is ___MASK86___ , a branch of internal medicine . Special features of endocrine glands are , in general , their ductless nature , their vascularity , and commonly the presence of intracellular vacuoles or granules that store their hormones . In contrast , exocrine glands , such as salivary glands , sweat glands , and glands within the gastrointestinal tract , tend to be much less vascular and have ducts or a hollow lumen . Syndrome of inappropriate antidiuretic hormone secretion ( SIADH ) is characterized by excessive release of antidiuretic hormone from the posterior pituitary gland or another source . The increase in blood volume ( hypervolemia ) often results in dilutional hyponatremia in which the plasma sodium levels are lowered and total body fluid is increased . It was originally described in people with small - cell carcinoma of the lung , but it can be caused by a number of underlying medical conditions . The treatment may consist of fluid intake restriction , various medicines , and management of the underlying cause . Salt administration may help prevent brain swelling by increasing attractive force to keep water in the bloodstream , preventing fluid buildup in tissue . SIADH was first described in 1957 . Hyponatremia , also spelled hyponatraemia , is a low sodium level in the blood . Symptoms can vary from none to severe . Mild symptoms include a decreased ability to think , headaches , nausea , and poor balance . Severe symptoms include confusion , seizures , and coma . Normal serum sodium levels are 135  145 mmol / L ( 135  145 mEq / L ). Hyponatremia is generally defined as a serum sodium level of less than 135 mmol / L and is considered severe when the level is below 120 mmol / L . The cause of hyponatremia is typically classified by a person ' s fluid status into low volume , normal volume , and high volume . Low volume hyponatremia can occur from diarrhea , vomiting , diuretics , and sweating . Normal volume hyponatremia is divided into cases with dilute urine and concentrated urine . Cases in which the urine is dilute include adrenal insufficiency , hypothyroidism , and drinking too much water or too much beer . Cases in which the urine is concentrated include syndrome of inappropriate antidiuretic hormone secretion ( SIADH ). High volume hyponatremia can occur from heart failure , liver failure , and kidney failure . Conditions that can lead to falsely low sodium measurements include high protein levels such as in multiple myeloma , high blood fat levels , and high blood sugar . Treatment is based on the underlying cause . Correcting hyponatremia too quickly can lead to complications . Rapid partial correction with 3 % normal saline is only recommended in those with significant symptoms and occasionally those in whom the condition was of rapid onset . Low volume hyponatremia is typically treated with intravenous normal saline . SIADH is typically treated with fluid restriction while high volume hyponatremia is typically treated with both fluid restriction and a diet low in salt . Correction , in those in whom the low levels have been present for more than two days should generally be gradual . Hyponatremia is one of the most commonly seen water  electrolyte imbalances . It occurs in about 20 % of those admitted to hospital and 10 % of people during or after an endurance sporting event . Among those in hospital hyponatremia is associated with an increased risk of death . The economic costs of hyponatremia are estimated at $ 2 . 6 billion in the United States . Heart failure ( HF ), often referred to as congestive heart failure ( CHF ), occurs when the heart is unable to pump sufficiently to maintain blood flow to meet the body ' s needs . Signs and symptoms commonly include shortness of breath , excessive tiredness , and leg swelling . The shortness of breath is usually worse with exercise , while lying down , and may wake the person at night . A limited ability to exercise is also a common feature . Chest pain , including angina , does not typically occur due to heart failure . Common causes of heart failure include coronary artery disease including a previous myocardial infarction ( heart attack ), high blood pressure , atrial fibrillation , valvular heart disease , excess alcohol use , ___MASK67___ , and cardiomyopathy of an unknown cause . These cause heart failure by changing either the structure or the functioning of the heart . There are two main types of heart failure : " heart failure due to left ventricular dysfunction " and " heart failure with normal ejection fraction " depending on whether the ability of the left ventricle to contract is affected , or the heart ' s ability to relax . The severity of disease is usually graded by the degree of problems with exercise . Heart failure is not the same as myocardial infarction ( in which part of the heart muscle dies ) or cardiac arrest ( in which blood flow stops altogether ). Other diseases that may have symptoms similar to heart failure include obesity , kidney failure , liver problems , anemia , and thyroid disease . The condition is diagnosed based on the history of the symptoms and a physical examination with confirmation by echocardiography . Blood tests , electrocardiography , and chest radiography may be useful to determine the underlying cause . Treatment depends on the severity and cause of the disease . In people with chronic stable mild heart failure , treatment commonly consists of lifestyle modifications such as stopping smoking , physical exercise , and dietary changes , as well as medications . In those with heart failure due to left ventricular dysfunction , angiotensin converting enzyme inhibitors or angiotensin receptor blockers along with beta blockers are recommended . For those with severe disease , aldosterone antagonists , or hydralazine with a nitrate may be used . Diuretics are useful for preventing fluid retention . Sometimes , depending on the cause , an implanted device such as a pacemaker or an implantable cardiac defibrillator may be recommended . In some moderate or severe cases cardiac resynchronization therapy ( CRT ) may be suggested or cardiac contractility modulation may be of benefit . A ventricular assist device or occasionally a heart transplant may be recommended in those with severe disease despite all other measures . Heart failure is a common , costly , and potentially fatal condition . In developed countries , around 2 % of adults have heart failure and in those over the age of 65 , this increases to 6  10 %. In the year after diagnosis the risk of death is about 35 % after which it decreases to below 10 % each year . This is similar to the risks with a number of types of cancer . In the United Kingdom the disease is the reason for 5 % of emergency hospital admissions . Heart failure has been known since ancient times with the Ebers papyrus commenting on it around 1550 BCE . Diarrhea , also spelled diarrhoea , is the condition of having at least three loose or liquid bowel movements each day . It often lasts for a few days and can result in dehydration due to fluid loss . Signs of dehydration often begin with loss of the normal stretchiness of the skin and irritable behaviour . This can progress to decreased urination , loss of skin color , a fast heart rate , and a decrease in responsiveness as it becomes more severe . Loose but non - watery stools in babies who are breastfed , however , may be normal . The most common cause is an ___MASK67___ of the intestines due to either a virus , bacteria , or parasite ; a condition known as gastroenteritis . These infections are often acquired from food or water that has been contaminated by stool , or directly from another person who is infected . It may be divided into three types : short duration watery diarrhea , short duration bloody diarrhea , and if it lasts for more than two weeks , persistent diarrhea . The short duration watery diarrhea may be due to an ___MASK67___ by cholera , although this is rare in the developed world . If blood is present it is also known as dysentery . A number of non - infectious causes may also result in diarrhea , including hyperthyroidism , lactose intolerance , inflammatory bowel disease , a number of medications , and irritable bowel syndrome . In most cases , stool cultures are not required to confirm the exact cause . Prevention of infectious diarrhea is by improved sanitation , clean drinking water , and hand washing with soap . Breastfeeding for at least six months is also recommended as is vaccination against rotavirus . Oral rehydration solution ( ORS ), which is clean water with modest amounts of salts and sugar , is the treatment of choice . Zinc tablets are also recommended . These treatments have been estimated to have saved 50 million children in the past 25 years . When people have diarrhea it is recommended that they continue to eat healthy food and babies continue to be breastfed . If commercial ORS are not available , homemade solutions may be used . In those with severe dehydration , intravenous fluids may be required . Most cases ; however , can be managed well with fluids by mouth . Antibiotics , while rarely used , may be recommended in a few cases such as those who have bloody diarrhea and a high fever , those with severe diarrhea following travelling , and those who grow specific bacteria or parasites in their stool . Loperamide may help decrease the number of bowel movements but is not recommended in those with severe disease . About 1 . 7 to 5 billion cases of diarrhea occur per year . It is most common in developing countries , where young children get diarrhea on average three times a year . Total deaths from diarrhea are estimated at 1 . 26 million in 2013  down from 2 . 58 million in 1990 . In 2012 , it was the second most common cause of deaths in children younger than five ( 0 . 76 million or 11 %). Frequent episodes of diarrhea are also a common cause of malnutrition and the most common cause in those younger than five years of age . Other long term problems that can result include stunted growth and poor intellectual development . Hypothyroidism , also called underactive thyroid or low thyroid , is a common disorder of the endocrine system in which the thyroid gland does not produce enough thyroid hormone . It can cause a number of symptoms , such as poor ability to tolerate cold , a feeling of tiredness , constipation , depression , and weight gain . Occasionally there may be swelling of the front part of the neck due to goitre . Untreated hypothyroidism during pregnancy can lead to delays in growth and intellectual development in the baby , which is called cretinism . Worldwide , too little iodine in the diet is the most common cause of hypothyroidism . In countries with enough iodine in the diet , the most common cause of hypothyroidism is the autoimmune condition Hashimoto ' s thyroiditis . Less common causes include : previous treatment with radioactive iodine , injury to the hypothalamus or the anterior pituitary gland , certain medications , a lack of a functioning thyroid at birth , or previous thyroid ___MASK75___ . The diagnosis of hypothyroidism , when suspected , can be confirmed with blood tests measuring thyroid - stimulating hormone ( TSH ) and thyroxine levels . Prevention at the population level has been with the universal salt iodization . Hypothyroidism can be treated with levothyroxine . The dose is adjusted according to symptoms and normalization of the thyroxine and TSH levels . Thyroid medication is safe in pregnancy . While a certain amount of dietary iodine is important , excessive amounts can worsen certain types of hypothyroidism . Worldwide about one billion people are estimated to be iodine deficient ; however , it is unknown how often this results in hypothyroidism . In the United States , hypothyroidism occurs in 0 . 3  0 . 4 % of people . Subclinical hypothyroidism , a milder form of hypothyroidism characterized by normal thyroxine levels and an elevated TSH level , is thought to occur in 4 . 3  8 . 5 % of people in the United States . Hypothyroidism is more common in women than men . People over the age of 60 are more commonly affected . Dogs are also known to develop hypothyroidism and in rare cases cats and horses can also have the disorder . The word " hypothyroidism " is from Greek " hypo -" meaning " reduced ", " thyreos " for " shield ", and " eidos " for " form ." Signs and symptoms . People with hypothyroidism often have no or only mild symptoms . Numerous symptoms and signs are associated with hypothyroidism , and can be related to the underlying cause , or a direct effect of having not enough thyroid hormones . Hashimoto ' s thyroiditis may present with the mass effect of a goiter ( enlarged thyroid gland ).