Receptor-mediated endocytosis

Introduction 

Diabetes Insipidus is a disease spreading worldwide at a very high rate. Diabetes Insipidus occurs due to the insufficient amount of ADH (antidiuretic hormone) in the body. This hormone is responsible for retaining water in the body. The hypothalamus produces this hormone. But, the pituitary gland stores and secretes ADH hormone, which is also called vasopressin.

The kidneys absorb a lot of water from urine before excretion. Due to this, the water level in the body does not fall. The process of absorption of water during urine formation is called selective reabsorption. It has great significance as it prevents dehydration by excessive loss.

Sometimes, there is less secretion of ADH; as a result, the cells of the kidneys fail to absorb the water. In some conditions, the kidney cells fail to respond to the ADH hormone. This causes a disturbance in the normal proportion of body fluids. ADH and Diabetes Insipidus are linked to each other through the maintenance of the proper osmotic balance of the body. 

Definition of ADH and Diabetes Insipidus

ADH- ADH (antidiuretic hormone) or vasopressin is responsible for maintaining an adequate amount of water in the body. Hypothalamus, a small portion of the brain situated below thalamus, secretes this hormone. However, the pituitary gland stores and secretes it.

Diabetes Insipidus- Diabetes Insipidus is a disorder in which there is lesser production of vasopressin, or the cells of the kidney fail to respond to it. This results in the higher production of dilute urine. It causes an imbalance in the metabolic concentration of salt and water in the body. 

Diabetes Insipidus Classification

There are four categories of Diabetes Insipidus:

1. Central Diabetes Insipidus- Central Diabetes Insipidus occurs due to a lack of ADH production by the hypothalamus. The deficiency limits the water-retaining capacity of the kidneys. This results in a large amount of urine production. The patient can become dehydrated. 

Central Diabetes Insipidus can be genetic or occur due to damage to the hypothalamus by head injuries. Other factors which contribute to this type of diabetes are tumours in the pituitary glands, brain surgery, Sheehan’s syndrome, and Langerhans cell histiocytosis.

1. Nephrogenic Diabetes Insipidus- As the name suggests, “nephro” is related to kidneys. In this type of diabetes, the ADH is secreted in a normal amount. Due to some underlying defects, the cells of the kidneys fail to respond to vasopressin. Thus, it eventually causes an increase in dilute urine formation.

The Nephrogenic Diabetes Insipidus may be genetic or occur due to some infection in the kidneys. Polycystic kidney diseases and high blood sugar levels are also responsible for the unusual behaviour of kidney cells towards ADH.

1. Gestational Diabetes Insipidus- Gestational Diabetes Insipidus is a rare condition occurring only in pregnant women. In this type, the placenta produces vasopressinase, an enzyme that destroys the ADH in mothers. However, the condition may only last for the gestational period. 
2. Primary Polydipsia (Dipsogenic Diabetes Insipidus)- In this condition, the mechanism of thirst is disturbed. It causes an excessive intake of fluids that eventually increases the production of diluted urine. The cause of primary polydipsia can be damage in the pituitary or some mental illness. 

Symptoms of Diabetes Insipidus

The common symptoms are as follows:

• Extreme thirst.
• Urination of more than 3 litres a day (polyuria).
• Uncontrolled urination (bed-wetting)
• Pale, colourless urine
• More dilute urine.
• Thirst for fluids such as cold drinks.
• Weakness
• Nausea
• Vomiting
• Dehydration due to frequent urination.

Diagnosis of Diabetes Insipidus

The tests for diagnosing Diabetes Insipidus are as follows:

• Water deprivation test- In this test, the doctors will prohibit you from drinking any fluids for some hours to examine the ADH content. As there is no intake of fluid, the level of water will decrease in the body. In normal conditions, the body will start producing more ADH for preventing dehydration. However, in the case of diabetes, there won’t be enough ADH to perform this function.

The doctors will measure the ADH level in the blood sample to conclude the result. 

• MRI (magnetic resonance imaging)- MRIs are responsible for checking any defects in the pituitary glands. It uses magnetic fields and radio waves for the detection of any defects in the brain and adjoining areas.
• Genetic Evaluation- The doctors will ask about the family history of such patients. People with diabetic parents or grandparents are more likely to have this disease. Therefore, it is necessary to evaluate the genetic line of diabetes. 

Treatment 

Diabetes is not completely curable, but it can be effectively managed through proper medication and a healthy diet. The treatment of Diabetes Insipidus depends upon the type. Therefore, the doctors first examine the type of diabetes then proceed with its treatment. 

Treatments of different types of diabetes are as follows:

• Central Diabetes Insipidus- As this type of diabetes is due to defects in the pituitary gland, the doctors try to treat the defect. You need to increase your water intake to stay hydrated. Moreover, doctors prescribe medicines that perform the function of ADH artificially. Desmopressin is an example of such a drug. It meets the need of ADH and prevents the loss of excess water in the form of urine. 

The doctors can give oral drugs, sprays, or injections as per the requirement of the patient. 

• Nephrogenic Diabetes Insipidus- In the case of this type of diabetes, the doctors will not rely on drugs like desmopressin. This type of diabetes involves the treatment of kidneys as kidneys are not responsive to ADH. The doctors will try to resolve the underlying cause of such unusual behaviour by kidney cells.

The doctors will prescribe medications such as hydrochlorothiazide (Microzide) for proper urine formation by kidneys. 

• Gestational Diabetes- Pregnant women, will have to take medicines like synthetic hormone desmopressin for the proper working of ADH in the body. However, this type of diabetes may resolve after childbirth.
• Primary Polydipsia (Dipsogenic Diabetes Insipidus)- This type of diabetes has no proper treatment. In the case of mental illness as the primary factor, the doctors will treat that cause. 

Conclusion 

ADH and Diabetes Insipidus are both interconnected. Shortage of ADH in the body is the primary cause of Diabetes Insipidus. The hypothalamus may fail to produce enough ADH, or the cells of kidneys may fail to respond to it. There are four types of Diabetes Insipidus.

Diabetes is not completely curable but can be effectively managed by proper medication and by maintaining a healthy diet. The most common symptom of Diabetes Insipidus is frequent and uncontrolled urination.