Diabetes insipidus is characterized by excessive thirst, excessive urination, large amounts of diluted urine, increased levels of sodium in the body, etc. The condition occurs due to a deficiency of the antidiuretic hormone vasopressin. Diabetes insipidus is often confused with diabetes mellitus, a more common metabolic disorder characterized by increased blood sugar levels and occurs due to a deficiency of pancreatic hormone (insulin). Whereas, in the case of diabetes insipidus, the blood sugar levels are within the normal range, and there is no lack of insulin in the body. Diabetes insipidus is a rare condition, and the common age of onset of the disease is between ten to 20 years.

What Is Diabetes Insipidus?

Diabetes insipidus is a disorder that is rare and presents with characteristic symptoms of excessive urination (polyuria) and excessive thirst (polydipsia). In an individual affected by diabetes insipidus, the kidneys cannot retain water, which causes an imbalance of water (fluids) and an imbalance of electrolytes, and salts in the body. This occurs due to a deficiency of a specific hormone called vasopressin, the antidiuretic hormone. Vasopressin is vital for the kidneys to regulate the water balance in the body. An average person produces about one to three quarts of urine per day (0.95 to 2.84 liters approx). But in the case of an individual with diabetes insipidus, this value may increase up to 20 quarts of urine (18.9 liters) per day.

What Causes Diabetes Insipidus?

Diabetes insipidus can occur due to any condition that affects the production, transportation, and release of the hormone vasopressin because disturbance in these activities will lead to vasopressin deficiency in the body, which is the primary cause of diabetes insipidus. The kidneys use vasopressin to regulate and balance the amount of water and fluids in the body. In some cases, there could be a problem in the part of the brain that controls thirst, which leads to an excessive amount of water intake, eventually causing diabetes insipidus.

What Are the Different Types of Diabetes Insipidus?

Based on the cause of the condition, diabetes insipidus can be of four types:

Central Diabetes Insipidus: Vasopressin is produced in the hypothalamus and stored in the posterior part of the pituitary gland. When the amount of fluids in the body is reduced, the pituitary gland releases vasopressin, which signals the kidneys to conserve fluids by pulling them from the urine and returning it to the blood circulation. However, in the case of central diabetes insipidus, there is a deficiency of vasopressin, and the kidneys fail to conserve fluids leading to an imbalance of fluids in the body. Therefore, central diabetes insipidus occurs when the body can not make an adequate amount of vasopressin. This may occur due to: any damage to the pituitary gland or the hypothalamus, tumors of the pituitary gland, head injury, autoimmune conditions (a condition in which the body’s immune system attacks healthy cells), or inflammation and infections.
Nephrogenic Diabetes Insipidus: In the case of nephrogenic diabetes insipidus, there is enough vasopressin production in the body, but the kidneys fail to respond to the hormone. There is a defect in the structure of the kidneys, which causes its ability to respond to vasopressin. This defect in the kidneys can occur due to; certain drugs, low serum potassium levels, low serum calcium levels, blockage in the urinary tract, chronic kidney diseases, etc.
Dipsogenic Diabetes Insipidus: This type of diabetes insipidus is also known as primary polydipsia. The hypothalamus is responsible for controlling the thirst-regulation mechanism in the body; there is an occurrence of dipsogenic diabetes insipidus. The problem with the hypothalamus causes a constant feeling of thirst, which leads to excessive drinking of water and, subsequently, excessive urination. Damage to the hypothalamus due to trauma or surgery, tumors, infections, certain drugs, etc., can lead to dipsogenic diabetes insipidus.
Gestational Diabetes Insipidus: This temporary condition develops during pregnancy. It is a rare condition, and it occurs when the mother’s placenta overproduces an enzyme that breaks down vasopressin. Women who are bearing twins and triplets in their wombs are more likely to develop gestational diabetes insipidus because they have more placental tissue.

What Are the Symptoms of Diabetes Insipidus?

The common signs and symptoms of diabetes insipidus include:

Is Diabetes Insipidus a Common Disease?

Diabetes insipidus is a rare condition, and the rate of occurrence is about one in 25,000 people globally. Both males and females are affected equally.

How Is Diabetes Insipidus Diagnosed?

Diabetes insipidus is diagnosed by studying the physical signs and symptoms of the patient, medical and family history, along with the presence of characteristic polyuria and polydipsia. A variety of blood and urine examinations are also done to evaluate the concentration of salt, electrolytes, and sugars. The following tests are done to confirm the diagnosis:

Urinalysis: A test of urine to detect a wide range of disorders. In the case of diabetes insipidus, the urinalysis will show over-dilution of the urine and the absence of sugar in the urine, which will mean the patient is not affected by diabetes mellitus.
Blood Examinations: The amount of sodium and calcium in the blood is evaluated.
Fluid or Water Deprivation Test: It is the definitive diagnostic test for diabetes insipidus, which determines the cause of the condition. During this test, the patient is asked not to drink water or any other fluid for several hours (four to eight hours approx), and then the amount of urine the patient passes is measured. The doctor will also monitor the weight and urine composition. Blood levels of vasopressin are also measured during this test. If there is no change in the water loss despite fluid deprivation, a synthetic form of vasopressin (Desmopressin) is given to the patient to distinguish between central diabetes insipidus and nephrogenic diabetes insipidus.
Imaging Test: MRI (magnetic resonance imaging) or CT scan (computed tomography) may be done to evaluate any damage to the hypothalamus or the pituitary gland or to check for the presence of any tumors in the brain.
Stimulation Test: During this test, the body is stimulated to produce vasopressin with the help of certain intravenous solutions. This is followed by measuring the blood levels of copeptin, a peptide that increases with an increase in the level of vasopressin.

How Is Diabetes Insipidus Treated?

In order to treat diabetes insipidus, it is important to ensure adequate fluid intake and reduction of urine output. The treatment varies depending on the cause of the condition and the severity of vasopressin deficiency in the body.

Central Diabetes Insipidus: In the case of partial central diabetes insipidus, with residual vasopressin activity, certain drugs like Hydrochlorothiazide may be useful in curing the condition. However, in the case of severe central diabetes insipidus with no vasopressin activity, a synthetic form of vasopressin known as Desmopressin is used as replacement therapy. Desmopressin may be injectable, taken orally, or in the form of a nasal spray.
Nephrogenic Diabetes Insipidus: In most cases, nephrogenic diabetes insipidus subsides when the underlying cause of the condition is treated. For example, drugs that may be causing the condition can be stopped or changed; chronic renal diseases should be treated; calcium and sodium levels should be balanced, the use of diuretic drugs to reduce urine output, etc.
Gestational Diabetes Insipidus: The condition usually subsides after the child's birth; however, during pregnancy, the doctor may prescribe Desmopressin as it is safe for the mother and the child.
Dipsogenic Diabetes Insipidus: There is no definitive treatment for the condition. However, sucking on ice and candies may increase the salivary flow and reduce the feeling of thirst. The doctor may advise Desmopressin in small doses to be taken at bedtime to reduce urination frequency at night.
Treatment for Children: Children affected by diabetes insipidus are given Hydrochlorothiazide along with water and formula milk. However, the use of Hydrochlorothiazide or Desmopressin should be done very cautiously because infants and children require a certain amount of water and fluid intake for their proper growth and development.

What Are the Complications of Diabetes Insipidus?

Diabetes insipidus can lead to the following complications if it is left untreated or if it is not treated properly. Common complications include:

Dehydration occurs because the body loses a lot of fluids and electrolytes.
Dehydration can lead to fainting, weakness, dizziness, dry mouth, altered mental alertness, etc.
Cardiovascular symptoms like an irregular heartbeat (arrhythmia).
Dry skin and dry mucous membranes.
Confusions, seizures, and changes in consciousness.
In very few cases, it can lead to comatose or coma (prolonged period of unconsciousness).
Sudden drop of blood pressure on standing or changing positions.

What Is the Difference Between Diabetes Insipidus and Diabetes Mellitus?

Diabetes insipidus is often mistaken to be similar to diabetes mellitus, a more common disorder, because of the similarity in the names of both conditions. Along with similar names, the two conditions have polyuria and polydipsia as their characteristic symptoms. However, the mechanism and cause of both disorders are entirely different. The difference between diabetes mellitus and diabetes insipidus are:

Diabetes Insipidus vs. Syndrome of Inappropriate Antidiuretic Hormone Secretion (SIADH)?

Conclusion:

Diabetes insipidus is a rare condition occurring due to a deficiency of the pituitary hormone vasopressin (antidiuretic hormone). Any condition that affects the production of vasopressin or blocks the action of vasopressin can lead to excessive urine production. The diagnosis and treatment of the condition require synthetic vasopressin (Desmopressin). The different types of diabetes insipidus require different types of treatment modalities. However, the condition is not severe or life-threatening and can be managed easily with proper treatment and precautions.