Central Diabetes Insipidus - Types, Causes, Symptoms, Complications, Diagnosis and Treatment

Introduction:

Central diabetes insipidus is a rare condition in which the kidneys excrete excess urine. "Insipid" means that which is colorless and odorless. The condition occurs due to a deficiency of a hormone called vasopressin or antidiuretic hormone (ADH). Though the name diabetes insipidus is similar to classic diabetes mellitus, both are two different conditions. There is an imbalance in the sugar levels of the body in diabetes mellitus, whereas an increase in water loss leading to dehydration is noticed in diabetes insipidus.

How Does Antidiuretic Hormone (ADH) Work?

ADH is produced in the hypothalamus, an area at the base of the brain. It is stored and released by the pituitary gland, a small pea-sized gland located below the hypothalamus. The hypothalamus is connected to the pituitary gland located below it through nerves. Baroreceptors are special cells located in the blood vessels that can sense a decrease in the blood volume, thereby triggering the release of ADH. Further, ADH directs the kidneys to reabsorb water from the urine, thereby increasing the blood volume, blood pressure, and urine concentration.

What Are the Effects of ADH Release?

ADH release causes the following effects on the body:

• An increase in the blood volume.

• An increase in blood pressure.

• Dilution of blood.

• Increase in blood osmolarity.

When the amount of ADH released is not enough to increase blood volume, a feeling of thirst is initiated that makes the affected person drink more water.

What Is Diabetes Insipidus?

Diabetes insipidus is when the body does not produce enough ADH, resulting in excess water loss through urine. The affected person experiences excessive thirst and a frequent urge to urinate. The amount of water excreted through urine is exceedingly high, which can be from 10 to 15 liters.

What Are the Types of Diabetes Insipidus?

There are two types of diabetes insipidus, namely:

1. Central Diabetes Insipidus (DI) - It occurs when the pituitary gland does not release sufficient ADH
2. Nephrogenic Diabetes Insipidus (NDI) - It occurs due to the inability of kidneys to respond to ADH.

What Are the Other Names of Central Diabetes Insipidus?

The other names of the condition include:

1. Pituitary diabetes insipidus.

2. Cranial diabetes insipidus.

3. Neurogenic diabetes insipidus.

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4. Neurohypophyseal diabetes insipidus.

What Are the Causes of Central Diabetes Insipidus?

The condition occurs mainly when there is damage to the hypothalamus or the pituitary gland. The following are the causes of central diabetes insipidus:

• Surgery.

• Injury.

• Inflammation (a condition in which a body part becomes red, swollen, and painful).

• Infection.

• Tumors.

• Genetic reasons (rare cause).

• A bulging artery, known as an aneurysm.

What Are the Symptoms of Central Diabetes Insipidus?

The signs and symptoms of central diabetes insipidus include:

1. Extreme thirst.

2. Excessive urine production. Urine produced is colorless and odorless.

3. Frequent urge to get up and pee at night.

Infants and young children present with the following signs and symptoms:

1. Bed-wetting.

2. Wet and heavy diapers.

3. Difficulty sleeping.

4. Loss of weight.

5. Fever.

6. Vomiting.

7. Constipation.

8. Delay in growth.

What Are the Complications of Central Diabetes Insipidus?

Central diabetes insipidus can cause complications like dehydration, an electrolyte imbalance, or a lack of sleep at night due to frequent urine passage, frequently known as nocturia.

Symptoms of dehydration include:

• Dry mouth.

• Increased thirst.

• Tiredness.

• Changes in the elasticity of the skin.

Symptoms of an electrolyte imbalance occur when the levels of sodium and potassium are altered, which include:

• Nausea.

• Severe vomiting.

• Muscle cramps.

• Loss of appetite.

• Confusion.

How Is Central Diabetes Insipidus Diagnosed?

The doctor diagnoses central diabetes insipidus based on medical history (that includes a family history), physical examination, and a group of tests. The doctor may order the following tests to confirm the diagnosis, which includes:

1. Urine Test: A urine sample is collected and sent to the lab for testing. The test helps to know if the urine is dilute or concentrated. The blood sugars measured in the urine sample can help differentiate diabetes insipidus from diabetes mellitus. Sometimes, the health care worker may order a 24-hour urine test in which urine is collected for a period of 24 hours and tested.

2. Blood Test: A blood sample is tested to know the levels of electrolytes (sodium and potassium) and also glucose levels.

3. Fluid Deprivation Test: In a fluid deprivation test, the person is advised not to drink anything for a period of time, and changes in body weight, blood sodium levels, and urine concentration are measured. This test assesses if the pituitary gland is releasing ADH in response to the absence of fluid intake. There are two types of the test which include:

• Short-Form Fluid Deprivation Test: The patient stops drinking fluids for a short period of time and collects the urine sample, which is then sent by the doctor to the lab for testing.

• Formal Fluid Deprivation Test: This test is done at the hospital to prevent complications of dehydration. After stopping fluids, the patient’s weight is noted, and a urine sample is collected every one to two hours until:

• The blood pressure falls too low.

• There is a rapid heartbeat upon standing.

• There is a five percent loss of body weight when compared to the starting body weight.

• Urine concentration increases.

4. Desmopressin (DDAVP) Challenge Test: This test is done as a continuation of a fluid deprivation test when the volume of urine excreted remains unchanged even after stopping fluids. The patient is administered Desmopressin, which differentiates between central and nephrogenic diabetes insipidus.

5. Magnetic Resonance Imaging (MRI) Scan: MRI scan of the brain helps detect any abnormalities in the hypothalamus or pituitary gland. It is a non-invasive method that uses magnetic fields and radio waves to construct pictures of soft tissues like the brain.

6. Genetic Screening: Screening of family members who had problems with excess urine production is done.

How Is Central Diabetes Insipidus Treated?

In patients with mild diabetes insipidus, increasing their water intake would suffice. However, if the doctor detects an abnormality in the hypothalamus or pituitary, correction of the abnormality is done.

Central diabetes insipidus can be treated with a synthetic hormone named Desmopressin (DDAVP, Nocturna). It is available in tablet form, injection, and a nasal spray. The medicine decreases urination by replacing the missing ADH. Some patients can make a small quantity of ADH. Desmopressin is prescribed accordingly to prevent complications from increased fluid retention in such patients.

Medicines like Chlorpropamide are advised to help make ADH more available to the body.

Conclusion:

A balance in the water levels has to be maintained for the proper functioning of the body. Water is the primary source of transport of minerals, proteins, and glucose to different body parts. Therefore, any changes in the body's functioning need to be addressed and diagnosed early. Central diabetes insipidus does not damage the kidneys. They continue to carry out their primary function of filtering blood. The patient must only be careful to prevent episodes of dehydration, always carry water along and wear “medic alert” jewelry to make people know about the condition. Treatment options to correct central diabetes insipidus help prevent severe complications.

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