Syndrome of inappropriate antidiuretic hormone (patient information)
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Syndrome of inappropriate antidiuretic hormone production 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, cancers, pulmonary diseases, and some drugs. Signs and symptoms 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, and 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. Adequate restriction of water intake and addition of a high concentration of sodium may get immediate improvement. Prognosis of SIADH varies widely, depending on the cause.
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?
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
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 morphin, antiepileptics, and some antidepressants medications.
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, cystic fibrosis, positive-pressure 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
- Diagnosis of SIADH is based on detailed history (especially drug history), clinical signs and symptoms, and extensive physical and neurological examination by a physician.
- Serum tests include electrolytes, BUN, creatinine, glucose levels, and osmolality. Patients with syndrome of inappropriate antidiuretic hormone may be characterized 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).
- Urine osmolality: would be greater than blood osmolality in SIADH
- Imaging Studies, such as X-ray, CT, and MRI may be help find the causes of syndrome of inappropriate antidiuretic hormone.
- Chest X-ray to look for ectopic causes of SAIDH and or CT Scan of the head and other suspected body area to located masses that may be secreting the hormone causing SIADH.
When to seek urgent medical care?
- Depending on the degree of the dilution hyponatremia, presentation of SIADH varies. It can be asymptomatic, or present with features of mild hyponatremia, such as:
- Syndrome of inappropriate antidiuretic hormone may be a clinical condition of diseases, such as cancers, drugs, and pulmonary diseases. When you have the diseases mentioned above, seek urgent medical care as soon as possible if you experience either of the following symptoms:
- Treatment is based on diagnostic findings and the level of hyponatremia. Removal of the offending medication and simple water restriction with some loop diuretic may suffice for treatment in patients with mild disease.
In patients with moderate to severe SIADH, water restriction may not improve symptoms. Drugs like conivaptan (an approved vasopressin receptors antagonist), lithium, and demeclocycline may be given to increase the plasma sodium level and diuretics to improve the excretion of free water. Patients can also receive hypertonic saline fluids intravenously to prevent central pontine myelinosis (a very severe complication of hyponatremia) in patients with severe hyponatremia.
- For immediate improvement, all patients with SIADH require sharp restriction of their daily water intake and addition an intravenous infusion of high sodium fluids (hypertonic saline solution). 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, then surgery, radiation therapy, or chemotherapy may be helpful.
- If SIADH resulted from drugs, then the patient must stop taking the medicine.
- If some infection may be the cause, the patient needs to control them by some antibiotics or other anti-microbiological drugs.
Where to find medical care for SIADH?
- Tell your doctor and monitor blood and urine levels of electrolytes and osmolality when taking drugs, such as:
What to expect (Outlook/Prognosis)?
- Prognosis of SIADH depends on the severity of the disease and the promptness of treatment.
- Prognosis of syndrome of inappropriate antidiuretic hormone (SIADH) also depends largely on its cause.
- Some of the complications of treatment of SIADH are including cerebral edema and entral pontine myelinolysis, which are seen with rapid sodium correction.