Merck Manual

Please confirm that you are not located inside the Russian Federation

honeypot link

Syndrome of Inappropriate Secretion of Antidiuretic Hormone (SIADH)

By

James L. Lewis III

, MD, Brookwood Baptist Health and Saint Vincent’s Ascension Health, Birmingham

Last full review/revision Sep 2021| Content last modified Oct 2021
Click here for the Professional Version
Topic Resources

The syndrome of inappropriate secretion of antidiuretic hormone develops when too much antidiuretic hormone (vasopressin) is released by the pituitary gland under certain inappropriate conditions, causing the body to retain fluid and lower the blood sodium level by dilution.

Vasopressin (also called antidiuretic hormone) helps regulate the amount of water in the body by controlling how much water is excreted by the kidneys. Vasopressin decreases water excretion by the kidneys. As a result, more water is retained in the body, which dilutes the level of sodium in the body. A low level of sodium in the blood is called hyponatremia Hyponatremia (Low Level of Sodium in the Blood) In hyponatremia, the level of sodium in blood is too low. A low sodium level has many causes, including consumption of too many fluids, kidney failure, heart failure, cirrhosis, and use of diuretics... read more .

The pituitary gland appropriately produces and releases vasopressin when the blood volume (amount of fluid in the blood vessels) or blood pressure goes down or when levels of electrolytes (such as sodium) become too high.

Secretion of vasopressin is termed inappropriate if it occurs when

When vasopressin is released in these situations, the body retains too much fluid, and the sodium level in blood decreases.

Causes of SIADH

Many conditions increase the risk of developing SIADH. SIADH may result when vasopressin is produced outside the pituitary gland, as occurs in some lung and other cancers. SIADH is common among older people and is fairly common among people who are hospitalized.

SIADH has a long list of possible causes that typically require additional tests to uncover.

Table
icon

Symptoms of SIADH

Diagnosis of SIADH

  • Blood and urine tests

Doctors suspect SIADH in people with hyponatremia that cannot be explained by other factors, such as pain, stress, strenuous exercise, a high blood sugar level, and certain disorders of the heart, thyroid gland, kidneys, or adrenal glands that can decrease blood volume and appropriately stimulate the release of vasopressin from the pituitary.

Blood and urine tests are done to measure the sodium and potassium levels and to determine how concentrated the blood and urine are (osmolality). Doctors also rule out other possible causes of excess vasopressin (such as pain, stress, drugs, or cancer).

Treatment of SIADH

  • Restriction of fluid intake

Intravenous fluids, including fluids containing very high concentrations of sodium (hypertonic saline), are sometimes given. Such treatments must be given carefully to avoid rapid increases in the sodium level.

If the sodium level in blood continues to decrease or does not increase despite restriction of fluid intake, doctors may prescribe drugs such as demeclocycline or lithium, which decrease the effect of vasopressin on the kidneys, or drugs such as conivaptan and tolvaptan, which block vasopressin receptors and prevent the kidneys from responding tovasopressin.

Drugs Mentioned In This Article

Generic Name Select Brand Names
No US brand name
VASOSTRICT
VAPRISOL
SAMSCA
LITHOBID
NOTE: This is the Consumer Version. DOCTORS: Click here for the Professional Version
Click here for the Professional Version
Others also read
Test your knowledge
Diabetic Ketoacidosis
Diabetic ketoacidosis is a complication of diabetes. It occurs mostly in people with type 1 diabetes. Diabetic ketoacidosis occurs when a lack of insulin prevents glucose in the bloodstream from entering the cells. Without adequate glucose, the cells burn fat for energy, producing compounds called ketones. Ketones supply some energy, but they also make the blood too acidic. There are several causes of ketoacidosis. Which of the following is a cause of ketoacidosis?
Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID

Also of Interest

Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID
TOP