Syndrome of inappropriate antidiuretic hormone secretionSIADH; Inappropriate secretion of antidiuretic hormone; Syndrome of inappropriate ADH release; Syndrome of inappropriate antidiuresis
Syndrome of inappropriate antidiuretic hormone secretion (SIADH) is a condition in which the body makes too much antidiuretic hormone (ADH). This hormone helps the kidneys control the amount of water your body loses through the urine. SIADH causes the body to retain too much water.
ADH is a substance produced naturally in an area of the brain called the hypothalamus. It is then released by the pituitary gland at the base of the brain.
The hypothalamus is an area of the brain that produces hormones that control:Body temperatureHeart rateHungerMoodRelease of hormones from many glands...Read Article Now Book Mark Article
There are many reasons why the body needs to make a lot of ADH. Common situations when ADH is released into the blood when it should not be produced (inappropriate) include:
- Medicines, such as certain seizure drugs, antidepressants, cancer drugs, opiates (less often), and heart, diabetes, and blood pressure drugs
- Surgery under general anesthesia
- Disorders of the brain, such as injury, infections, and stroke
- Brain surgery in the region of the hypothalamus
- Tuberculosis, cancer, chronic infections, and lung disease, such as pneumonia
- Substance abuse
Rare causes include:
- Rare diseases of the hypothalamus or pituitary
- Leukemia and cancer of the small intestine, pancreas, and brain
- Mental disorders
With SIADH, the urine is very concentrated. Not enough water is excreted and there is too much water in the blood. This dilutes many substances in the blood such as sodium. A low blood sodium level is the most common cause of symptoms of too much ADH.
Low blood sodium level
Low blood sodium is a condition in which the sodium level in the blood is lower than normal. The medical name of this condition is hyponatremia....Read Article Now Book Mark Article
Often, there are no symptoms from a mildly low sodium level. More symptoms occur the lower the level of the sodium.
When symptoms do occur, they may include any of the following:
- Nausea and vomiting
- Problems with balance that may result in falls
- Mental changes, such as confusion, memory problems, strange behavior
- Seizures or coma, in severe cases
A seizure is the physical changes in behavior that occurs during an episode of abnormal electrical activity in the brain. The term "seizure" is often...Read Article Now Book Mark Article
Exams and Tests
The health care provider will perform a complete physical examination to help determine the cause of your symptoms. Establishing fluid status (dehydrated, volume overload, normal volume) is an important part of making the correct diagnosis.
Lab tests that can confirm and help diagnose low sodium include:
- Comprehensive metabolic panel (includes blood sodium)
Comprehensive metabolic panel
A comprehensive metabolic panel is a group of blood tests. They provide an overall picture of your body's chemical balance and metabolism. Metaboli...Read Article Now Book Mark Article
- Osmolality blood test
Osmolality blood test
Osmolality is a test that measures the concentration of all chemical particles found in the fluid part of blood. Osmolality can also be measured with...Read Article Now Book Mark Article
- Urine osmolality
The osmolality urine test measures the concentration of chemicals in urine. Osmolality can also be measured using a blood test.Read Article Now Book Mark Article
- Urine sodium and potassium
The sodium urine test measures the amount of sodium the urine. Sodium can also be measured in a blood sample.Read Article Now Book Mark Article
- Toxicology screens for certain medicines
- Lung and brain imaging tests in children suspected of having SIADH
ADH can be measured in the blood, but is difficult to process for many labs and takes up to two weeks to get a result. Serum co-peptin can be used to estimate the ADH level in the blood.
Treatment depends on the cause of the problem. For example, surgery is done to remove a tumor producing ADH. Or, if a medicine is the cause, its dosage may be changed or another medicine may be tried.
In all cases, the first step is to limit fluid intake. This helps prevent excess fluid from building up in the body. Your provider will tell you what your total daily fluid intake should be. The restriction is not just for water, but for almost all fluids (coffee, tea, juice, soda, etc.).
If you have severe symptoms, it is a medical emergency. This is usually treated with salt solution (3% saline) given through an IV into the veins (intravenous) in the hospital.
Medicines may be needed to block the effects of ADH on the kidneys so that excess water is excreted by the kidneys. These medicines may be given as pills or as injections given into the veins.
Outcome depends on the condition that is causing the problem. Low sodium that occurs rapidly, in less than 48 hours (acute hyponatremia), is more dangerous than low sodium that develops slowly over time. When sodium level falls slowly over days or weeks (chronic hyponatremia), the brain cells have time to adjust and the acute symptoms such as brain swelling don't occur. Chronic hyponatremia is associated with nervous system problems such as poor balance and poor memory. Many causes of SIADH are reversible. Rapid correction of chronic hyponatremia can also cause dangerous complications (osmotic demyelination).
Osmotic demyelination syndrome (ODS) leads to brain cell dysfunction. It is caused by the destruction of the layer (myelin sheath) covering nerve ce...Read Article Now Book Mark Article
In severe cases, low sodium can lead to:
- Decreased consciousness, hallucinations or coma
- Brain herniation
When to Contact a Medical Professional
When your body's sodium level drops too much, it can be a life-threatening emergency. Call your provider right away if you have symptoms of this condition.
Atteih S, Ratner J. Endocrinology. In: Kleinman K, Mcdaniel L, Molloy M, eds. The Harriet Lane Handbook. 22nd ed. Philadelphia, PA: Elsevier; 2021:chap 10.
Hannon MJ, Thompson CJ. Vasopressin, diabetes insipidus, and the syndrome of inappropriate antidiuresis. In: Jameson JL, De Groot LJ, de Kretser DM, et al, eds. Endocrinology: Adult and Pediatric. 7th ed. Philadelphia, PA: Elsevier Saunders; 2016:chap 18.
Verbalis JG. Disorders of water balance. In: Yu ASL, Chertow GM, Luyckx VA, Marsden PA, Skorecki K, Taal MW, eds. Brenner and Rector's The Kidney. 11th ed. Philadelphia, PA: Elsevier; 2020:chap 15.
Review Date: 5/13/2021
Reviewed By: Brent Wisse, MD, Board Certified in Metabolism/Endocrinology, Seattle, WA. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.