What to Know About Antidiuretic Hormone Function and Testing
But too much ADH, and your kidneys retain too much water, causing dangerously low sodium levels. This is a symptom of the syndrome of inappropriate antidiuretic hormone release (SIADH).
ADH testing can determine if the level of ADH in your blood is lower or higher than a laboratory standard value. However, another medical condition is usually the root cause of atypical ADH levels, so usually additional testing is necessary to identify it and determine the appropriate treatment.
This article will explain more about ADH and its functions, ADH testing, and how to treat ADH-related conditions. It will also discuss high and low ADH and what they mean.
The major function of ADH is to regulate the amount of water that the kidneys produce as urine. ADH allows the kidneys to take back, or reabsorb, water from urine.
Water goes back into your body’s tissues and bloodstream, and your urine becomes more concentrated. ADH maintains a good balance of fluid in your body. This maintains blood volume and blood pressure. ADH is also known as arginine vasopressin.
Since ADH works on the kidneys, it may be surprising to learn that special nerve cells make it in the hypothalamus, which is as the base of the brain.
Nerve cells transport the hormone to the posterior pituitary gland, just below the hypothalamus. The pituitary releases it into the bloodstream in response to certain signals from elsewhere in the body.
Regulation of ADH secretion is complex. Specialized proteins known as receptors act as sensors in the large blood vessels and the heart. They are also called baroreceptors. Baroreceptors detect changes like low blood pressure or blood volume and send a message to the brain.
There are two types of baroreceptors: low pressure volume receptors and high pressure arterial baroreceptors. Stretching blood vessel walls activates both receptors. The baroreceptors send a signal to the brain, triggering ADH release into the bloodstream.
The released ADH acts on the kidneys, causing them to excrete less water from the blood they filter. ADH acts specifically on the nephron in each kidney, the cellular part of the kidneys that filters blood and forms urine.
Antidiuretic hormone testing is a way of measuring the level of ADH in the blood. The test requires a small sample of blood, usually from a vein puncture from your inside elbow.
A healthcare professional may want to know your ADH level in case of the following symptoms:
- symptoms of diabetes insipidus and dehydration, which can include:
- symptoms of low sodium, which can include:
Contact a medical professional for any of the symptoms listed above, especially if there is no other explanation for them. For instance, if you drink a lot of fluids and you are still thirsty, call your doctor.
If your ADH level falls outside the typical reference range for the laboratory, your doctor may recommend other tests to find out the exact cause of your symptoms.
When your ADH levels are too high, your body produces less urine. This fluid retention means your cells have too much water and not enough sodium. This is what happens in people with SIADH. Their bodies release ADH sporadically, sometimes far more than their bodies need.
There are different situations when the brain may release too much ADH, such as:
- infection of the brain
- brain injury that affects the hypothalamus
- effects after surgery from a general anesthetic
- substance use disorder
- chronic health conditions like infections, cancer, and tuberculosis
Very high levels of ADH can cause fluid imbalances and low sodium levels that can lead to swelling of the brain or seizures. These conditions can be life threatening. Get medical help straight away for neurological symptoms.
Low ADH means the hypothalamus is not producing it or the pituitary gland is not secreting it. Low ADH causes central diabetes insipidus. This produces similar symptoms as diabetes, but it does not have to do with glucose metabolism.
When ADH is low, the kidneys produce more urine. People with diabetes insipidus often have low ADH levels. This causes them to drink excess water and always feel thirsty. Possible causes of low ADH include damage or diseases that affect the pituitary gland or hypothalamus, and excessive or compulsive water drinking.
Contact your healthcare professional if you experience excessive thirst and frequent urination. Your doctor may recommend ADH and other tests to evaluate your blood and urine for fluid imbalances.
Diabetes insipidus can also occur if ADH secretion is unchanged but the kidneys become resistant to its effects. This is nephrogenic diabetes insipidus. There are inherited causes of the nephrogenic type. Certain medications, such as lithium and tetracycline, can cause it as well.
Treatment options for ADH-related conditions depend on low or high ADH levels.
For SIADH, which results in too much ADH and low sodium levels, treating the underlying cause may cure SIADH. To increase sodium levels, balance electrolytes, and prevent complications, treatment may include:
- limiting fluid intake to reduce the buildup of fluid in the body
- taking medications, including:
- furosemide (Lasix), a diuretic, which reduces fluid buildup
- demeclocycline, which inhibits ADH
- vasopressin antagonist receptors like tolvaptan (Samsca, Jynarque) and conivaptan (Vaprisol) in severe, persistent cases of SIADH
For central diabetes insipidus due to low ADH, doctors prescribe desmopressin. This medication acts like ADH to lower sodium levels.
For nephrogenic diabetes insipidus, your doctor may prescribe an alternative remedy for you and recommend that you stop the medicine.
Eating foods that contain less salt may also help. Your doctor may also suggest you reduce the consumption of protein-rich foods like meat, eggs, and processed foods.
The outlook for ADH-related conditions will depend on the underlying cause. Speak with your doctor for the best line of treatment. Do not take any medication, change your medicine, or alter your diet without speaking with your doctor first.
Below are some questions people asked about ADH.
What is ADH release?
ADH release means the secretion of ADH from the posterior pituitary gland into the bloodstream. The brain often initiates the production of ADH in response to high sodium concentration and to regulate blood volume and pressure.
How does ADH regulate blood pressure?
ADH regulates blood pressure by acting on the blood vessels and kidneys. When the blood volume and blood pressure are too low, baroreceptors in the heart and large blood vessels sense a decreased stretch in the arteries. This sends a signal to the brain to increase the production of ADH.
Another way ADH regulates blood pressure is by conserving fluid volume, causing less urine production.
What stimulates ADH?
Low blood pressure or low blood volume caused by dehydration or blood loss will stimulate the release of ADH. Special sensors in the blood vessels and heart detect these changes in blood volume and pressure and send a signal to the brain, which stimulates the release of ADH.
ADH is a small molecule that the hypothalamus makes and the pituitary gland secretes. ADH plays a vital role in maintaining the body’s fluid and electrolyte balance. Changes in ADH levels can cause serious health conditions.
An ADH test is a blood test that can help diagnose ADH-related conditions like diabetes insipidus and SIADH. ADH-related conditions are often treatable with the right medications and dietary and lifestyle changes.