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{{Syndrome of inappropriate antidiuretic hormone (patient information)}}

{{CMG}} {{APM}}; '''Associate Editor-In-Chief:''' {{OO}} Jinhui Wu, M.D.

==Overview==
Syndrome of inappropriate antidiuretic hormone production (SIADH) is a condition in which the body develops an excess of water and a decrease in [[sodium]] concentration. It may be caused by central nervous system diseases, [[cancer]]s, [[pulmonary disease]]s and some drugs. Signs and aymptoms vary widely. Some patients with SIADH may become severely ill, or may have no symptoms at all. Usual symptoms include [[nausea]], [[vomiting]], [[loss of appetite]], [[fatigue]], [[weakness]],even [[consciousness disorder]]s.  Blood tests of [[hyponatremia]] ([[sodium]] <135 mEq/L) and low serum [[osmolality]] (<280 mOsm/kg) may prompt the diagnosis of SIADH. Treatment depends on the causes. Sharp restriction of water intake and addition of a high concentration of sodium may get immediate improvement. Prognosis of SIADH varies widely, depending on the causes.

Syndrome of inappropriate antidiuretic hormone secretion often presents with clinical features of low blood level of sodium (i.e. hyponatremia). It is the most common cause of hyponatremia seen in clinical practice, as hyponatremia is the most common electrolyte abnormality seen in clinical medicine.
SIADH arises when there is inappropriate secretion of the antidiuretic hormone that cause the kidneys to retain free water rather than excreting it leading to fluid accumulation in the body with low blood level of sodium.  The low level of sodium is due to the dilution effect of excess free body water and not a shortage; therefore, treatment of low sodium level in SIADH is geared towards removing the excess free water and improving the level of sodium.

==What are the symptoms of SIADH?==
Symptoms vary, depending on the degree of abnormality in the serum [[sodium]] concentration and the speed with which this concentration falls. Usual symptoms include: 

:*[[Nausea]], [[vomiting]]
:*[[Loss of appetite]]
:*[[Fatigue]] and [[weakness]] 
:*[[Irritability]]
:*Personality changes, such as combativeness.
:*[[Seizures]]
:*[[Confusion]]
:*[[Hallucination]]s
:*[[Stupor]]
:*[[Coma]]

Other health problems may also cause these symptoms. Only a doctor can tell for sure. A person with any of these symptoms should tell the doctor so that the problems can be diagnosed and treated as early as possible.

==Diseases with similar symptoms==
:*[[Adrenal insufficiency]]
:*[[Diabetic Ketoacidosis]]
:*[[Hyperglycemia]]
:*[[Pseudohyponatremia]]
:*[[Psychogenic polydipsia]]
:*[[Hypopituitarism]]
:*[[Hypothyroidism]] or [[myxedema coma]]

==What causes SIADH?==

The causes of SIADH are many, and because the disease may present with features of electrolyte disturbances, there are many non-associated diseases that present like SIADH. 
The most common cause of SIADH is ectopic secretion of the antidiuretic hormone (also called arginine vasopressin) by cancer cells. Cancers like lung or bronchogenic cancers, lymphoma(s) in any location, head and neck cancers, sarcoma and myriad of other cancers can cause SIADH.
Other causes of SIADH include: Pulmonary diseases, central nervous system disorders, as well as pharmacotherapy with anticancer drugs like vincristine, cyclophosphamide; opioids like morphine, antiepileptic and some antidepressants medications.

==Who is at highest risk?==
:*Central nervous system disease: [[Brain tumor]]s, [[trauma]], [[infection]] such as [[meningitis]] and [[encephalitis]], [[Guillain-Barré syndrome]], [[delirium tremens]], [[multiple sclerosis]] 
:*Pulmonary disease: [[Small cell lung cancer]], [[pneumonia]], [[chronic obstructive pulmonary disease]], [[lung abscess]], [[tuberculosis]], [[cystisc fibrosnis]], positive-apressure ventilation
:*[[Cancer]]: [[Lung cancer]], [[pancreas cancer]], [[thymoma]], [[ovarian cancer]], [[lymphoma]], [[laryngeal cancer]], [[Nasopharyngeal carcinoma]], [[bladder cancer]], [[prostate cancer]], [[breast cancer]], [[melanoma]].
:*[[Drug]]s: [[Nonsteroidal anti-inflammatory drug]]s, [[nicotine]], [[diuretic]]s, [[chlorpropamide]], [[carbamazepine]], [[tricyclic antidepressant]]s, [[selective serotonin reuptake inhibitor]]s, [[vincristine]], [[thioridazine]], [[cyclophosphamide]], [[clofibrate]], [[bromocriptine]], [[haloperidol]], [[thiothixene]], exogenous [[oxytocin]].
:*[[Surgery]]: Damage to the [[hypothalamus]] or [[pituitary gland]] during or after [[surgery]]
:*[[Idiopathic]]

==When to seek urgent medical care?==
Syndrome of inappropriate antidiuretic hormone may be a clinical condition of diseases such as cancers, damages and pulmonary diseases. When you have the diseases mentioned above, you should be alert of the appearance the signs of syndrome of inappropriate antidiuretic hormone. If you experience either of the following symptoms, seek urgent medical care as soon as possible: 

:*[[Dehydration]]
:*Consciousness disorders, such as [[confusion]], [[hallucination]]s, [[stupor]] or [[coma]].

==Diagnosis==
:*Serum tests include electrolytes, BUN, creatinine, glucose levels, and osmolality. Patients with syndrome of inappropriate antidiuretic hormone may be characterised with [[hyponatremia]] ([[sodium]] <135 mEq/L) and low serum [[osmolality]] (<280 mOsm/kg).
:*Urine tests: Patients with syndrome of inappropriate antidiuretic hormone show elevated urinary [[sodium]] level (>20 mmol/L) and urine osmolality (generally >100 mOsm/L).
:*Imaging Studies, such as [[x-ray]], [[CT]] and [[MRI]] may be help find the causes of syndrome of inappropriate antidiuretic hormone.

==Treatment options==
Treatment of syndrome of inappropriate antidiuretic hormone depends on the cause. 
 
:*For immediate improvement, all patients with SIADH require sharp restriction of their daily water intake and addition an intravenous infusion of fluid with a high concentration of sodium. (hypertonic saline solution). And, patients may be treated with diuresis to promote water excretion.
:*The most definitive way to relieve SIADH is to deal with the underlying problem itself. If SIADH resulted from [[cancer]]s,  [[surgery]], [[radiation therapy]], or [[chemotherapy]] may be helpful. If SIADH produced by [[drug]]s, then the patient must stop taking the medicine. If some infection may be the cause, the patient needs to controlling them by some [[antibiotics]] or other anti-microbiological drugs.

==Where to find medical care for SIADH?==
[http://maps.google.com/maps?f=q&amp;hl=en&amp;geocode=&amp;q={{urlencode:{{#if:{{{1|}}}|{{{1}}}|syndrome of inappropriate antidiuretic hormone}}}}&amp;sll=37.0625,-95.677068&amp;sspn=65.008093,112.148438&amp;ie=UTF8&amp;ll=37.0625,-95.677068&amp;spn=91.690419,149.414063&amp;z=2&amp;source=embed Directions to Hospitals Treating syndrome of inappropriate antidiuretic hormone]

==What to expect (Outlook/Prognosis)?==
The prognosis of Syndrome of inappropriate antidiuretic hormone (SIADH) depends largely on its cause. If the cause is [[drug]]s, SIADH usually improves after stopping a [[drug]]. If SIADH is assiciated with some [[infection]], treating the infection may be important. For those SIADH with [[cancer]]s, the outcomes may be poor.

==Prevention==
:*Tell your doctor and monitor blood and urine levels of [[electrolyte]]s and [[osmolality]] when taking drugs such as [[nonsteroidal anti-inflammatory drug]]s, [[nicotine]], [[diuretic]]s, [[chlorpropamide]], [[carbamazepine]], [[tricyclic antidepressant]]s, [[selective serotonin reuptake inhibitor]]s, [[vincristine]], [[thioridazine]], [[cyclophosphamide]], [[clofibrate]], [[bromocriptine]], [[haloperidol]], [[thiothixene]], exogenous [[oxytocin]].

==Sources==
http://www.nlm.nih.gov/medlineplus/ency/article/000314.htm

[[Category:Endocrinology patient information]]
[[Category:Endocrinology]]
[[Category:Nephrology patient information]]
[[Category:Nephrology]]
[[Category:Patient information]]
[[Category:Mature chapter]]
[[Category:Overview complete]]
[[Category:For review]]

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