It is a condition that results from insufficient production of antidiuretic hormone, a hormone that helps the kidneys and body conserve the correct amount of water.
Normally, the antidiuretic hormone controls the urine production of the kidneys.
This hormone is produced by the hypothalamus, which is a small gland at the base of the brain.
This hormone is stored in the pituitary gland and is then released by the neurohypophysis into the bloodstream, in amounts appropriate to the needs of the body at any given time, due to the responses of the physiological stimuli of the neurohypophyseal neurons.
Antidiuretic hormone is secreted to decrease the amount of urine output, so that dehydration does not occur.
Diabetes insipidus, however, causes excessive production of very dilute urine and excessive thirst.
Types of diabetes insipidus
The disease is categorized into groups. Three of the groups are described below:
Central diabetes insipidus
It is characterized by insufficient production or secretion of antidiuretic hormone and can be partial or total.
This insufficiency can be the result of damage to the pituitary gland or hypothalamus caused by head injuries, genetic disorders, tumors, surgery, and other conditions such as meningitis or inflammation.
In children, the most common cause is usually an inherited genetic disease, but in many cases the cause of diabetes insipidus is an unknown disease.
Nephrogenic diabetes insipidus
It is the lack of renal response to normal levels of antidiuretic hormone, it can be caused by drugs such as democycline and lithium or chronic disorders, such as kidney failure, sickle cell disease or polycystic kidney disease.
It occurs when there is a defect in the renal tubules.
Renal structures cannot respond adequately to vasopressin secretion, even though it is normal.
Gestational diabetes insipidus
This type of diabetes insipidus is associated with pregnancy and automatically resolves after delivery.
During pregnancy, an enzyme that is originated by the placenta destroys the anti-diuretic hormone produced by the mother.
Primary polydipsia is also known as psychogenic polydipsia or dipogenic diabetes insipidus, which is due to an inappropriate increase in thirst, due to an alteration of the neural mechanisms that regulate plasma osmolarity and thirst.
The cause is more associated with excessive fluid intake, than a difficulty with the production of anti-diuretic hormone or some injury.
An inappropriate increase in excessive fluid intake, which is due to an alteration in the neural mechanisms responsible for regulating plasma osmolarity and thirst.
Causes of diabetes insipidus
Diabetes insipidus is caused by partial or complete insufficiency of arginine vasopressin.
This deficiency is generally caused by damage to the hypothalamus or the pituitary gland.
In very rare cases, vasopressin deficiency arises from a genetic mutation inherited as an autosomal dominant or recessive trait.
The hypothalamus releases neurohormones that intervene in the secretion of other hormones, which help in the regulation of metabolic processes such as growth, reproductive function and the autonomous functions of the organism.
Vasopressin is secreted by the hypothalamus, which travels through nerve fibers to the pituitary gland.
It is stored in the neurophysis and is released into the bloodstream when the body needs it.
Vasopressin goes to the kidneys. Once there, it attaches itself to receptor proteins located on the surface of some kidney cells.
At this time, the process by which the kidneys reabsorb water in the body begins.
Without adequate levels of vasopressin, water is not reabsorbed and is lost in the urine.
Researchers have determined that some cases of inherited diabetes insipidus are caused by disruptions or mutations in the arginine vasopressin gene.
Mutations in the arginine vasopressin gene impair vasopressin synthesis or secretion.
Researchers believe that some cases of idiopathic diabetes insipidus may be caused by autoimmune factors.
Autoimmune disorders occur when the body’s natural defenses against “foreign” or invading organisms begin to attack healthy tissue for unknown reasons.
In diabetes insipidus, the body makes antibodies or lymphocytes that attack cells that secrete vasopressin.
Diabetes insipidus can also occur as part of a larger syndrome or disorder that includes Wolfram syndrome or septo-optic dysplasia.
Other disorders that can cause central diabetes insipidus include:
- Accidental damage done during surgery to the hypothalamus or pituitary gland.
- A brain injury, particularly a skull base fracture.
- A tumor.
- Sarcoidosis (a rare inflammation of the lymph nodes and other tissues throughout the body) or tuberculosis.
- An aneurysm (a bulge in the wall of an artery) or a blockage in the arteries leading to the brain.
- Some forms of encephalitis or meningitis.
- The rare disease of Langerhans cell histiocytosis.
Symptoms of diabetes insipidus
Symptoms of diabetes insipidus can show up over time or come on abruptly.
The main characteristic of diabetes insipidus is excessive thirst (polydipsia) and excessive urination (polyuria), even at night (nocturia).
The progression and severity of diabetes insipidus varies from patient to patient.
Some patients have a severe form of diabetes insipidus with little or no vasopressin activity.
And other patients may show a mild form of the disease, with moderate vasopressin activity.
Symptoms in babies include lethargy, vomiting, irritability, constipation, and fever.
They may also experience fatigue, bed-wetting, stunted growth, and weight loss.
If infants with diabetes insipidus are not treated, concurrent dehydration can lead to brain damage, developmental delays, seizures, and mental and physical retardation.
People with diabetes insipidus may develop in addition to dehydration and symptoms such as abnormal heart rates, fever, confusion, seizures, orthostatic hypotension with the presence of dizziness or momentary loss of consciousness (syncope), dry skin and mucous membranes, and potentially eat.
However symptoms that are indicative of diabetes insipidus include:
- However excesiva.
- Excessive urine production.
The symptoms of diabetes insipidus may resemble other conditions or medical problems.
The person can drink large amounts of fluid, 3 to 30 liters per day, to make up for the fluid that is lost in the urine.
When compensation is not possible, dehydration can quickly follow, resulting in low blood pressure that can trigger shock.
The person continues to urinate large amounts of urine, and this excessive urination is particularly noticeable at night.
Diagnosis of diabetes insipidus
When a diagnosis is made, diabetes insipidus may be suspected based on specific characteristics such as thirst and excessive urination.
Accompanied by a complete physical evaluation, detailed medical history of the patient and specialized tests to confirm the diagnosis.
Your doctor may recommend additional tests to confirm the diagnosis and rule out other underlying conditions.
Blood and urine tests
Doctors will recommend blood and urine tests to determine the concentration of salts and glucose in the samples.
The urine is tested for sugar first to rule out diabetes mellitus (a more common cause of excess urination).
Blood tests show abnormal levels of many electrolytes, including a high level of sodium.
The vasopressin assay
Affected individuals may receive a diagnostic injection of the hormone arginine, vasopressin, or a vasopressin analog such as desmopressin to determine the response of the kidneys.
Individuals with a different form of diabetes insipidus, such as nephrogenic diabetes insipidus, do not respond to the administration of vasopressin supplements because in nephrogenic diabetes insipidus, the kidneys are resistant to the effects of vasopressin.
In contrast, people with diabetes insipidus respond to this treatment with supplemental vasopressin.
Water deprivation test
In some individuals, an additional test, known as a water deprivation test, may be required to confirm a diagnosis.
During this test, affected people cannot ingest any kind of liquid and can only eat dry food for a period of time.
In this water deprivation test, blood and urine samples will be taken to measure serum sodium or osmolality and urine output.
Urine output, blood electrolyte levels, and weight are measured regularly over a period of approximately 12 hours.
This dehydration provides a stimulus for vasopressin secretion that can be estimated by measuring copeptin concentrations or by urine concentration.
Serum vasopressin levels can also be measured if properly managed.
A doctor monitors the person’s condition during the course of the test.
Body weight and vital signs are monitored to prevent excessive dehydration.
Once the 12 hours have elapsed, or earlier in exceptional cases where the patient in the monitoring shows a decrease in blood pressure, an increase in heart rate or a loss of more than 5% in the patient’s body weight, the doctor proceeds to inject vasopressin.
This test confirms the diagnosis of central diabetes insipidus if, in response to the application of vasopressin, the excessive urination of the patient stops, there is a higher concentration in the urine, the blood pressure increases, and the heartbeat is normal.
This test is used to distinguish between the various causes of diabetes insipidus.
It is the best way to diagnose central diabetes insipidus.
The diagnosis of nephrogenic diabetes insipidus is made if after injection, excessive urination continues, urine remains dilute, and blood pressure and heart rate do not change.
X-rays, CT or MRI are used to rule out a possible cause of brain tumors that may affect the pituitary gland.
A common MRI finding in children with central diabetes insipidus is the absence of the “bright spot” in the posterior saddle, which is normally believed to represent vasopressin-containing neurons.
Treatment of diabetes insipidus
Reducing excessive urine production and ensuring adequate fluid intake is essential.
Specific treatment for diabetes insipidus will be determined by the physician based on the following factors:
- The age, general health, and medical history of the patient.
- The extent of the disease.
- Tolerance of specific medications, procedures, or therapies.
- The severity of vasopressin deficiency.
- Expectations for the course of the disease.
The underlying cause of the disease should be treated, whenever possible.
Treatment may include modified antidiuretic hormone medications given as injections, pills, or intranasal spray.
Medications that are commonly used for the treatment of nephrogenic diabetes insipidus are:
- Anti-inflammatory drugs such as indomethacin (Inacid).
- Diuretic drugs, such as hydrochlorothiazide, combined with amined (Ameride).
- Desmopressin (1-deamino-8-D-arginine vasopressin) a synthetic form of vasopressin.
Desmopressin is a long-acting form of vasopressin, which can be given as a nasal spray twice a day and sometimes as a tablet or as an injection under the skin or intravenously.
The dose is adjusted until the body’s water balance and normal urine production are maintained.
Overuse of vasopressin can cause swelling caused by fluid retention and other problems in the body.
People with central diabetes insipidus who have surgery or are unconscious usually receive injections of vasopressin.
Patients with partial diabetes insipidus and residual vasopressin activity may be treated with medications such as chlorpropamide, clofibrate, carbamazepine, clofibrate, and thiazide diuretics that stimulate vasopressin production.
These drugs are unlikely to completely relieve symptoms in people with severe diabetes insipidus.
Nephrogenic diabetes insipidus, when caused by medications such as lithium, must be discontinued to restore normal kidney function in the body.
Hereditary nephrogenic diabetes insipidus or lithium-induced diabetes insipidus are treated by drinking plenty of fluids.
The expulsion of urine is combined with medications that decrease urine production.
Babies with diabetes insipidus are particularly troublesome and can be treated by diluting the formula with water and hydrochlorothiazide.
Desmopressin should be used with caution in this age group as babies have a required liquid intake to provide adequate calories for growth.
In cases where diabetes insipidus is of hereditary origin, genetic counseling can be very useful for the affected people and their family environment as prevention.