What Is SIADH?

Medically Reviewed by Jabeen Begum, MD on August 25, 2022
Written by Sarah Vallie
4 min read

You’ve probably seen advertisements for sports drinks that claim to not only hydrate you but also replenish your electrolytes. In some cases, though, too much fluid can be a bad thing and actually cause your body to lose electrolytes. 

SIADH is one of those cases. 

Syndrome of inappropriate antidiuretic hormone secretion (or, SIADH) is a condition in which your body produces too many antidiuretic hormones.

Antidiuretic hormones help the kidneys regulate the levels of water and salt in the body and help blood vessels constrict. As a result, they help control urine production and blood pressure. Like many other hormones, the antidiuretic hormone is made in the brain’s hypothalamus and secreted by the pituitary gland.

When your body has too much antidiuretic hormone, that can cause you to retain water and experience a deficit in electrolytes. Electrolytes are minerals inside your body that carry an electric charge. The most common electrolytes in your body include sodium, magnesium, potassium, calcium, chloride, phosphate, and bicarbonate. 

You get electrolytes from food and drink and lose them through urine and sweat. Low levels of electrolytes may cause fatigue, nausea, headache, and muscle cramps.

There are many things that may cause your body to overproduce antidiuretic hormones. Most commonly, SIADH occurs in those with heart problems or in those with diseases of the hypothalamus. Some cancers, especially cancer in the lungs, may produce antidiuretic hormones.

Other causes of SIADH include:

  • Head trauma
  • Brain tumors
  • Damage to the brain during surgery
  • Meningitis, a condition in which the membranes of the brain and spinal cord become swollen, usually due to an infection
  • Encephalitis, a condition in which the active tissue of the brain is inflamed due to an infection or autoimmune response
  • Lung disease
  • Guillain-Barre syndrome, a condition in which your immune system attacks your nerves and can lead to paralysis
  • HIV, or human immunodeficiency virus, a virus that attacks the body’s immune system and can eventually lead to AIDS
  • Low levels of thyroid hormones, which control your body’s metabolism
  • Low levels of parathyroid hormones, which control the calcium levels of your blood
  • Genetics
  • Psychosis

SIADH results in very concentrated urine and too much water in the blood.

Many of the symptoms of SIADH are due to low enzyme levels, and they are therefore the same as the symptoms of low enzyme levels. Severe cases of SIADH may include symptoms such as: 

  • Nausea and vomiting
  • Tremors and muscle cramps
  • Irritability
  • Depression
  • Trouble with memory
  • Confusion
  • Hallucinations
  • Trouble with balance
  • Seizures
  • Coma

These symptoms can have many other causes, so if you begin experiencing these symptoms, contact a doctor right away.

When you visit your doctor, they’ll likely get your health history and possibly take a look at your family’s health history as well.

To confirm a diagnosis of SIADH, your doctor will need to take blood and urine samples. With these samples, your doctor will take a look at the levels of sodium and potassium in your body. They’ll also take a look at the osmolality of your blood and urine. Osmolality is the amount of substances dissolved in the blood and urine. 

Your doctor may also decide to run a comprehensive metabolic panel as well.

Treatment for SIADH will depend on several factors. Your doctor will look at:

  • Your age
  • Your health
  • Your medical history
  • The extent of your SIADH
  • Your ability to handle medications, procedures, and therapies
  • Your comfort level with various treatments

For most people with SIADH, the first step in treatment is to limit fluid intake. This is to prevent excess fluid buildup within your body. This doesn’t just mean limiting water, but instead, most beverages, including coffee, tea, soda, and juice.

If you are experiencing severe symptoms, you will need to be treated with saline through an IV.

Further treatment may depend on what’s causing your SIADH. Chronic SIADH may require treatments such as:

  • Medications to inhibit antidiuretic hormone
  • Medications to regulate the volume of your body fluid
  • Surgery may be required to remove a tumor

The outcome for your SIADH will depend on the cause of your SIADH. In many cases, the causes of SIADH are reversible.

Low sodium levels, or hyponatremia, can cause major issues in the body, especially if it occurs rapidly. When your sodium levels drop over time, your body has time to adjust, and brain swelling doesn’t usually occur. However, when sodium levels drop suddenly, it can become dangerous. 

Severe cases of low sodium may lead to hallucinations, loss of consciousness, coma, brain herniation, and death. Brain herniation is a condition in which pressure causes your brain tissue to move. In this case, the pressure would be a result of swelling in the brain from low sodium.

Unfortunately, if your hyponatremia occurred slowly but is corrected too quickly, that may lead to a condition called osmotic demyelination syndrome. In this condition, the myelin sheath that covers the nerve cells is destroyed, causing your nerves to no longer properly transmit signals.

Unfortunately, the symptoms of SIADH are very similar to the symptoms of so many other medical conditions. Some of these conditions are mild, but others are very severe. To be safe, if you experience any symptoms of SIADH, your best option is to talk to your doctor. 

In most cases, SIADH is reversible, but in cases of sudden drops of sodium, it can be lethal. Early intervention is always the best way to prevent lasting complications of SIADH.