Fatigue, memory lapses, and feeling less steady on your feet are all common in older age. However, they shouldn’t be dismissed as “normal aging,” and all of them warrant contacting your doctor.
One problem that can cause symptoms like these is something you might not have heard of—hyponatremia, a condition in which you have too much water relative to the amount of sodium in your blood. The most common cause of hyponatremia in older adults is syndrome of inappropriate antidiuretic hormone secretion (SIADH).
What Is SIADH?
SIADH is a condition that leads to low sodium levels in the body and is caused by trouble with regulating how much water is in the body. This problem occurs when the body manufactures too much antidiuretic hormone (ADH). Also known as vasopressin, ADH controls the amount of water in your body. It is produced in the hypothalamus (an area of the brain responsible for manufacturing numerous hormones that control body functions) and stored in the pituitary gland, which also produces important hormones.
“The hypothalamus constantly monitors how much water is in the blood and signals the pituitary gland to release small amounts of ADH into the blood on a steady basis, with adjustments as needed,” explains Holly M. Koncicki, MD, MS, a Mount Sinai nephrologist. “The ADH travels through the bloodstream to the kidneys, where it regulates urination.”
If the hypothalamus detects too much water in your blood—which may happen if you’ve been drinking large amounts of fluids—it signals the pituitary gland to release less ADH or no ADH at all. “In this scenario, the kidneys excrete more water, meaning that you will pass a greater volume of more dilute urine,” Dr. Koncicki says. If the hypothalamus detects that your blood contains too little water (which may happen if you are dehydrated due to vomiting and diarrhea, or are sweating heavily during exercise), it signals the pituitary gland to release more ADH. “When the hormone reaches the kidneys, it signals them to return water to the blood instead of passing it into the urine,” Dr. Koncicki explains. “In this scenario, urine becomes more concentrated and you will urinate less often until your blood becomes sufficiently dilute again.”
Once your blood concentration is back within its normal range, ADH release should return to its usual pattern. But sometimes this process does not happen—ADH continues to be released, and the body retains too much water.
This situation is potentially harmful because of how it affects your sodium levels. You probably are aware that too much sodium contributes to high blood pressure and other cardiovascular issues. But low sodium levels also are a problem, since sodium helps regulate the amount of water inside cells. Extra fluid in the blood means that blood sodium levels become proportionately too low, resulting in hyponatremia. This phenomenon causes most of the symptoms seen with SIADH because it triggers the movement of water from your blood into your cells.
“The excess water causes cells to swell, but while most cells in the body can tolerate some swelling, the cells in the brain are less able to because they are enclosed within the skull and have little space to expand,” Dr. Koncicki says. “At some point, therefore, swelling of the brain cells begins to interfere with brain function, resulting in symptoms.”
SIADH Symptoms
Hyponatremia causes the symptoms seen in SIADH. “It is possible for sodium levels in the blood to decrease slowly, over weeks or months, and in these circumstances, the symptoms may be subtle enough to be dismissed as age-related changes or misdiagnosed as cognitive impairment,” Dr. Koncicki says. “A more rapid or prolonged drop in sodium will result in more significant symptoms.”
SIADH symptoms may include:
- Headaches
- Nausea and vomiting
- Fatigue, lack of energy, and drowsiness
- Muscle cramps
- Difficulty focusing, irritability, and confusion
- Drowsiness
- Unsteady walking and/or falls
- Seizures
What Causes SIADH?
A range of conditions can cause SIADH, either by causing ADH to be produced elsewhere in the body or by stimulating the release of ADH. As an example, ADH may be produced by some types of cancer, particularly lung cancer. “The tumor actually manufactures ADH, thus bypassing the normal system of ADH regulation in the hypothalamus,” Dr. Koncicki says. “In another example, problems with the brain or nervous system—such as stroke, head injuries, bleeding in the brain, and brain tumors—can interfere with the hypothalamus or pituitary gland in a way that causes ADH to be released continuously even though the hormone is not needed.”
Prolonged ADH release also can occur due to stress, such as that caused by nausea, serious illness, respiratory infections, pain, and surgery. “In situations like this, ADH may be released inappropriately because stress hormones trigger the brain to prioritize maintaining your blood circulation and blood pressure,” Dr. Koncicki explains. “Both depend on blood volume, which, in turn, depends on the fluid content of your blood.”
Other SIADH causes include medication side effects. Certain drugs—including antidepressants like citalopram (Celexa), duloxetine (Cymbalta), fluoxetine (Prozac), and sertraline (Zoloft)—can stimulate the release of ADH. Other medications, including nonsteroidal inflammatory drugs like ibuprofen (Advil, Motrin) and naproxen (Aleve, Naprosyn), can enhance the kidneys’ response to ADH so that even normal levels of the hormone prompt the kidneys to retain more water. “Older adults are especially vulnerable to drug interference with ADH regulation because they often take multiple medications,” Dr. Koncicki notes.
How Is SIADH Diagnosed?
In making a SIADH diagnosis, your doctor will review your medications to ensure that they are not contributing to your symptoms. Blood and urine tests probably will be performed to check your sodium level and evaluate how concentrated your blood and urine are. Your thyroid hormone levels also may be assessed, since hypothyroidism (underactive thyroid) can cause hyponatremia and your doctor will want to rule out the condition as an underlying cause of your symptoms. You also may undergo imaging tests to look for causes like lung cancer, stroke, and brain injuries.
How Is SIADH Treated?
SIADH treatment depends on the underlying cause and how unbalanced your sodium levels are. If a specific underlying cause is identified, it will be treated—for example, you’ll undergo treatment for an infection, or a medication may be changed or adjusted. Your doctor may recommend limiting your fluid intake, which helps your sodium levels recover, or, if necessary, prescribe medications that increase water excretion.
“In severe cases, people may need to be admitted to the hospital, where they can receive intravenous sodium under medical supervision,” Dr. Koncicki adds. “Most people do recover from SIADH, although those whose condition is related to a serious illness or cancer may need long-term monitoring.”
When to Seek Medical Help
SIADH symptoms warrant a call to your doctor. Even if it turns out that SIADH is not the cause, you and your healthcare team probably can manage whatever is ailing you in a way that improves your well-being and quality of life.
Dr. Koncicki recommends seeking immediate medical attention if you or a loved one develops more serious SIADH symptoms, including loss of mental clarity, extreme drowsiness, seizures, and loss of consciousness. “Swift diagnosis of SIADH is crucial in older adults and can help prevent potentially serious complications,” she says.
