Syndrome of inappropriate antidiuretic hormone (patient information)

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 * Associate Editor-In-Chief: 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. Iy may be caused by central nervous system diseases, cancers, pulmonary diseases 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 disorders. 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.

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
 * Hallucinations
 * 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 most common cause of ectopic ADH secretion is cancer. Certain lung cancers, as well as some head and neck tumors, are the most common cancers that cause this problem. In rare cases, many other tumors may cause ectopic ADH secretion.

Who is at highest risk?

 * Central nervous system disease: Brain tumors, 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.
 * Drugs: Nonsteroidal anti-inflammatory drugs, nicotine, diuretics, chlorpropamide, carbamazepine, tricyclic antidepressants, selective serotonin reuptake inhibitors, 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, seeking urgent medical care as soon as possible:


 * Dehydration
 * Consciousness disorders, such as confusion, hallucinations, 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 cancers, surgery, radiation therapy, or chemotherapy may be helpful. If SIADH produced by drugs, 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?
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 drugs, SIADH usually improves after stopping a drug. If SIADH is assiciated with some infection, treating the infection may be important. For those SIADH with cancers, the outcomes may be poor.

Prevention

 * Tell your doctor and monitor blood and urine levels of electrolytes and osmolality when takind drugs such as nonsteroidal anti-inflammatory drugs, nicotine, diuretics, chlorpropamide, carbamazepine, tricyclic antidepressants, selective serotonin reuptake inhibitors, vincristine, thioridazine, cyclophosphamide, clofibrate, bromocriptine, haloperidol, thiothixene, exogenous oxytocin.