What Is Central Diabetes Insipidus?

Central diabetes insipidus (CDI) is a rare disorder characterized by excessive thirst—or polydipsia—and excessive urination—or polyuria—that occur as a result of damage to the pituitary gland.

The pituitary gland in the brain releases the hormone arginine vasopressin (AVP)—also known as antidiuretic hormone (ADH)—which acts on the kidneys to help promote water reabsorption.

When the pituitary gland is damaged via surgery, tumor, head injury, or illness, deficiencies of ADH arise and the free water regulatory mechanism between the brain and kidney is disrupted. Without appropriate secretions of ADH, the kidneys are unable to concentrate urine.

A person with central diabetes insipidus usually passes an abnormally high amount of urine and feels the need to drink more water to replace the fluid they have lost as a result.

Types of Central Diabetes Insipidus

CDI is classified into three subtypes: 

• Idiopathic
• Secondary
• Familial

Idiopathic Central Diabetes Insipidus

Idiopathic CDI means that the cause or reason for the loss or ineffectiveness of the arginine vasopressin hormone is unknown. Some research points to CDI’s link to vascular central nervous system damage, but the relationship between the two has never been perfectly understood.

Secondary Central Diabetes Insipdius

Antidiuretic hormone acts to maintain blood pressure, blood volume, and tissue water concentration by controlling the amount of water in the body by concentrating urine in the kidneys. This mechanism is disrupted when secondary causes disrupt the pituitary system. 

Secondary CDI makes up two-thirds of CDI cases. Tumors in the central nervous system such as craniopharyngioma and germ cell tumors are the most frequent causes of secondary CDI. Other causes of secondary CDI include:

• Brain tumors (especially craniopharyngioma) and cerebral metastasis (with the most common being lung cancer and leukemia/lymphoma)
• Neurosurgery (usually after the removal of large adenomas)
• Traumatic brain injury
• Pituitary bleeding
• Subarachnoid hemorrhage
• Pituitary ischemia (e.g., Sheehan syndrome, ischemic stroke)
• Infection (such as meningitis)

Familial Central Diabetes Insipidus

This hereditary form of CDI is rare, but in some cases genetics may play a major role.

Familial CDI is inherited mostly in an autosomal dominant mode, and preliminary research shows that the number of causal mutations in the AVP gene exceeds 80. Some researchers also believe that there may be a connection between autoimmune disease and CDI, but more research needs to be done to elucidate this connection. 

Symptoms of Central Diabetes Insipidus

The main symptoms of central diabetes insipidus are excessive urination and thirst, but symptoms of dehydration may also occur if you are losing more water than you are taking in.

Excessive water loss in the urine can be between 10 to 15 liters a day, so drinking large amounts of water is vital to stay hydrated if you are not taking medication.

Causes of Central Diabetes Insipidus

Diabetes insipidus (DI) is a condition in which the kidneys are unable to concentrate urine. Central DI—the most common form of diabetes insipidus—is caused by insufficient levels of circulating antidiuretic hormone.

When you have insufficient ADH, you are more likely to excrete large quantities of diluted urine—or polyuria—which causes excessive thirst—or polydipsia—in response to fluid loss.

You may also develop the need to urinate at night—or nocturia—leading to sleep deprivation and daytime sleepiness.

Diagnosis of Central Diabetes Insidipus

The diagnosis of CDI is made based on your history of symptoms and confirmatory tests performed by your practitioner or another healthcare provider.

Diagnosis of CDI is based on the following:

• Medical and family history
• Physical exam
• Urinalysis
• Blood tests
• Fluid deprivation test
• Magnetic resonance imaging (MRI)

If CDI is suspected, sodium, plasma osmolality, and urine osmolality values are tested.

An endocrinologist or primary care doctor may perform a water deprivation test. This allows CDI to be differentiated from other issues that may throw off your water regulatory system or primary polydipsia.

If the water deprivation test is inconclusive or you are in need of another confirmatory test, you may be given desmopressin. Your response to desmopressin is important because CDI, which occurs in the brain, must be distinguished from nephrogenic diabetes insipidus (NDI), which occurs when receptors on the kidney do not respond to ADH.

If CDI—that is, a lack of ADH—is the cause of your body’s fluid imbalance, then your ability to concentrate should be corrected. If taking desmopressin does not correct the problem, then your diabetes insipidus may be due to NDI or non-functional ADH receptors on the kidneys, or some other cause.

If CDI is diagnosed, a CT scan or MRI of the head should be conducted to rule out brain tumors, especially craniopharyngioma, germ cell tumors, or cancer metastasis.

Treatment

Desmopressin or DDAVP, a synthetic vasopressin analog, is the treatment of choice in central DI. It works by replacing the vasopressin (also known as ADH) that your body normally produces.

Desmopressin is usually prescribed as an oral pill that is taken two to three times per day. The medication may also come as an injection or nasal spray. Your healthcare provider may start you on a low dose and slowly increase in accordance with your symptom relief. 

When taking desmopressin, keep four things in mind to avoid side effects and maximize the positive effects of the drug:

• Try to take your medication at the same time every day
• Follow the directions on the prescription label
• Take desmopressin exactly as directed
• Ask your practitioner, a healthcare professional, or a pharmacist to explain any part of the drug regimen that you do not understand 

If your endocrinologist identifies secondary causes of CDI, treatment of the underlying disease will usually result in the resolution of your symptoms. 

Of note, this treatment helps you to manage your symptoms of central diabetes insipidus; however, it does not cure the disease.

Prognosis

Serious complications from CDI are rare. The main complication is dehydration if fluid loss is greater than liquid intake, but it is usually corrected by drinking more water.

Still, you should be aware of symptoms of dehydration and treat them immediately. If left untreated, severe dehydration can lead to:

• Seizures
• Permanent brain damage
• Even death

A Word From VeryWell

If you have a mild case of CDI, the only treatment is to drink more water. Even if it is caused by a small tumor, your healthcare provider may not suggest removal if it is not growing in size or impacting your vision or sense of smell.

In some cases, your practitioner may prescribe desmopressin, which controls urine output, maintains fluid balance, and prevents dehydration. You may have to follow a special diet and limit the amount of fluid you drink so that the drug is maximally effective. These small changes, while not always easy to implement, can help you live a happy and healthy life.