SIADH (Syndrome of Inappropriate Antidiuretic Hormone Secretion)

SIADH causes your body to hold onto too much water. This can lower the sodium level in your blood and lead to symptoms such as headaches, nausea, weakness, or confusion.

SIADH stands for syndrome of inappropriate antidiuretic hormone secretion. To understand what happens with SIADH, it helps to know what antidiuretic hormone (ADH) normally does.

ADH is a hormone that helps control the amount of water in your body. It’s made in your brain and released into your blood by the pituitary gland when your body needs to hold onto water

ADH tells your kidneys to return more water to your bloodstream instead of removing it through your urine. As a result, you make less urine, and your urine becomes more concentrated.

For example, when you’re dehydrated, your body releases more ADH to help you hold onto water. ADH levels can also rise when your blood pressure or blood volume drops.

Once your body has enough water, ADH levels normally fall. Your kidneys can then remove more water through your urine.

With SIADH, your body keeps telling your kidneys to hold onto water even when it doesn’t need to.

The extra water dilutes the sodium in your blood. This causes a low sodium level called hyponatremia.

Your kidneys are usually working normally with SIADH. The problem is the signal they’re getting. Too much ADH tells your kidneys to keep water when your body should be getting rid of it.

Several health problems can cause SIADH. Conditions that affect the brain can interfere with normal ADH levels. These include:

• Stroke
• Head injury
• Infection
• Brain tumors

Lung problems can also cause SIADH. These include pneumonia and other lung conditions.

Some cancers can cause SIADH as well. Small cell lung cancer is one cancer that has a strong link to the condition.

Certain medications may also cause SIADH or lead to low sodium levels. These include some antidepressants, seizure medications, and cancer treatments.

Surgery, severe illness, and pain can also cause your body to release more ADH.

You usually don’t feel the effects of too much ADH itself. Instead, symptoms develop when your sodium gets too low.

Symptoms may include:

• Headache
• Nausea or vomiting
• Fatigue
• Weakness
• Trouble concentrating
• Confusion
• Muscle cramps

How quickly your sodium drops also matters. A sudden or severe drop can affect the brain and cause serious symptoms.

Seizures, severe confusion, extreme drowsiness, or loss of consciousness require emergency medical care.

Your doctor will use blood and urine tests to look for signs of SIADH.

A blood test can check your sodium level. It may also measure serum osmolality, which shows how concentrated or diluted your blood is.

Your doctor may also test your urine. With SIADH, your urine often stays more concentrated than expected even though your blood has become too diluted.

Other tests can check your kidney, thyroid, and adrenal function. This helps rule out other conditions that can cause low sodium.

If your doctor diagnoses SIADH, you may need more tests to find the cause. This could include looking at your medications or checking for an underlying lung, brain, or other medical condition.

Treatment depends on how low your sodium is, your symptoms, and what’s causing SIADH.

For mild or stable SIADH, your doctor may ask you to limit how much fluid you drink. This can help bring your sodium level back up.

If limiting fluids isn’t enough, your doctor may recommend other treatments that help your body remove extra water.

Treatment also focuses on the cause of SIADH. Your doctor may adjust a medication or treat an underlying illness that’s causing your body to release too much ADH.

You’ll likely need blood tests during treatment to check your sodium level. Sodium needs to rise at a safe rate. Raising it too quickly can cause serious complications.

Severe hyponatremia that causes significant symptoms needs hospital treatment. Doctors may give a concentrated salt solution through an IV to carefully raise your sodium level while monitoring you closely.

SIADH can cause your sodium level to fall too low, so getting the right diagnosis and treatment is important. Treatment can safely raise your sodium while your doctor looks for and treats the cause of SIADH

If you’ve been diagnosed with SIADH or low sodium, schedule an appointment with our San Antonio team to discuss your symptoms, testing, and treatment options.

1. Is SIADH a Kidney Problem?

No. Your kidneys are usually working normally with SIADH. The problem is that too much ADH tells your kidneys to hold onto water when your body doesn’t need it.

2. Can SIADH Go Away?

Yes, sometimes. SIADH may go away when the cause is treated or stops. For example, SIADH caused by a medication, surgery, or short-term illness may improve.

If an ongoing health problem is causing SIADH, you may need longer-term treatment.

3. Should You Drink Less Water if You Have SIADH?

Your doctor may ask you to limit how much fluid you drink as part of your SIADH treatment. How much you should drink depends on your condition and sodium level.

Don’t restrict fluids on your own unless your doctor tells you to.

4. Does SIADH Mean You Have Cancer?

No. Cancer is one possible cause of SIADH, but there are many others. These include certain medications, lung infections, conditions that affect the brain, surgery, and other illnesses.

Small cell lung cancer is one type of cancer that can cause SIADH.