What is SIADH?
SIADH is the syndrome of inappropriate antidiuretic hormone secretion. It is a rare condition in which the body makes too much antidiuretic hormone (ADH), resulting in water retention in the body and decreased sodium levels in the blood.
Antidiuretic hormone (ADH), also called vasopressin, is produced in the brain by the hypothalamus gland. The hormone is then stored in and released by the pituitary gland. ADH hormone helps kidneys conserve the correct amount of water in the body, hence regulating the way the body eliminates and conserves water. When ADH is produced in excess, it results in SIADH. SIADH can be due to a problem in the hypothalamus or other causes and triggers. It can occur at any age and is seen more often in children.SIADH makes it difficult for the body to eliminate water. Water retention in the body leads to decreased levels of electrolytes, such as sodium. The condition of low sodium levels in the body is called hyponatremia. Hyponatremia is responsible for many of the symptoms of SIADH and can result in serious complications. Treatment is usually conservative, involving limiting fluid intake and medication to reduce water retention and ADH levels. Treatment of the underlying cause of SIADH is also required.
What causes SIADH?
- Infection and inflammation of the brain
- Bleeding in or around the brain
- Injury to the head
- Hydrocephalus (fluid accumulation in the brain)
- Guillain-Barre syndrome (a condition in which the immune system attacks the nerves)
- Multiple sclerosis (a disease in which the immune system damages the protective covering of nerves)
- Generalized infections, such as HIV and Rocky Mountain spotted fever
- Cancers of the lung or gastrointestinal or genitourinary tract lymphoma, sarcoma
- Lung infection, such as pneumonia
- Cystic fibrosis (an inherited life-threatening disorder that damages the lungs and digestive system)
- Certain medications and anesthesia
- Hereditary factors
What are the signs and symptoms of SIADH?
SIADH makes it difficult for the body to release excess water and as a result there is accumulation of fluid in the body and hyponatremia (low sodium levels). Fluid retention and hyponatremia are responsible for many of the signs and symptoms of SIADH. The symptoms may be mild and vague at first and may go unnoticed. However, the symptoms can become more severe. In severe cases, the following signs and symptoms may be present
- Irritability and restlessness
- Loss of appetite
- Muscle cramps
- Muscle weakness
- Nausea and vomiting
- Mental confusion
- Memory problems
- Changes in personality
- Hallucinations (experiencing things that are not present)
- Stupor (a serious mental state where people don't respond to conversation and only to physical stimulation, such as to pain or rubbing on their chest)
How is SIADH diagnosed?
The doctor will ask for the medical history and conduct a physical examination of the patient. A blood test to check the ADH levels and electrolytes levels would be done and a urine sample would also be taken. Imaging studies (such as magnetic resonance imaging or MRI) may be done to rule out bleeding or tumors in the brain.
What is the treatment and prognosis for SIADH?
The treatment involves limiting fluid intake to avoid further buildup. Medications to reduce water retention (such as diuretics) and inhibit ADH may include Lasix (furosemide) and Demeclocycline. The underlying medical conditions triggering SIADH would also be treated. The prognosis will depend on the cause of SIADH. If untreated, it can lead to respiratory failure, coma and death.
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