Difference Between Diabetes Mellitus and Diabetes Insipidus

Main Difference – Diabetes Mellitus vs Diabetes Insipidus

Diabetes Mellitus and Diabetes Insipidus are two different medical conditions which arise due to a dysregulation of the endocrine system. Even though they share several similar features, the pathophysiology behind them has significant differences depending on the fundamental etiology and the progression of the pathological changes. The main difference between diabetes mellitus and diabetes insipidus is that diabetes insipidus involves a problem with the production of antidiuretic hormone or kidney’s response to antidiuretic hormone (nephrogenic diabetes insipidus), whereas diabetes mellitus is caused by a deficiency of the pancreatic hormone insulin.

This article covers,

1. What is Diabetes Mellitus?
     – Definition, Cause, Signs and Symptoms, Diagnosis, Treatment

2. What is Diabetes Insipidus?
     – Definition, Cause, Signs and Symptoms, Diagnosis, Treatment

3. What is the difference between Diabetes Mellitus and Diabetes Insipidus?

What is Diabetes Mellitus

Diabetes Mellitus is a long term ailment of metabolism that includes Diabetes type 1 and 2 which occur due to a malfunctional pancreas which fails to secrete required amounts of Insulin or poorly functioning insulin either due to an inherent pathology or acquired condition later in life, respectively. It can also happen as a result of excessive blood glucose, which does not respond to the secreted amount of insulin due to a separate mechanism known as Insulin resistance.

There are 2 types of Diabetes:

Type 1 Diabetes

Type 1 diabetes is a condition occurring due to the destruction of pancreatic Beta cells by autoimmune cells in the body. The patients rely on insulin injection since the body is not able to produce its own insulin. This condition can affect individuals at any age but mostly seen before 20 years.

Type 2 Diabetes

Individuals with type 2 diabetes produce Insulin which is either not enough up to the level of required concentration or cells regulating glucose levels are resistant to the insulin produced by pancreatic B cells. Also known as Adult onset diabetes, this condition mostly affects individuals over 40 years of age.

Signs and Symptoms

• Increased frequency of urination (polyuria)
• Increased thirst (polydipsia)
• Increased hunger (polyphagia)
• Increased frequency of urination at night (Nocturia)
• Loss of weight and muscle bulk
• Weakened immune system
• Poor would healing

Long-term Complications

• Diabetic neuropathy
• Diabetic retinopathy
• Diabetic nephropathy

Treatment

Initial intervention for Diabetes include,

• Lifestyle modifications such as consuming a healthy diet, cutting down of carbohydrates and sugars, increased intake of proteins, physical exercises and reduction of weight in obese individuals.
• Pharmacological management – Metformin treatment and Insulin injections.

Additionally, it is important to carry out annual screening tests in order to check vision, neurological functioning and kidney functions for the early detection of Diabetic complications.

Diabetic foot care is also important to prevent wounds (due to neuropathy and poor wound healing capacity) which can get complicated by serious life-threatening conditions such as septicemia.

What is Diabetes Insipidus

This is a condition characterized by excessive thirst and excreting large volumes of severely dilute urine with a significant reduction of fluid intake which has no effect on the concentration of the urine.

There are various types of Diabetes Insipidus, depending on the etiology.

• Neurological form (central DI-CDI) – Due to a deficiency of arginine vasopressin (AVP) or antidiuretic hormone (ADH).
• Nephrogenic diabetes Insipidus (NDI) – Due to dysfunctional kidneys or nephrons caused by an insensitivity to ADH.
• Some rare causes of this condition include gestational, alcohol and drug abuse.

Pathophysiology

Our body consists of a complex system created in order to balance the volume and composition of body fluids. This system is made up of kidneys which filter extra body fluids from the blood circulation and bladder which stores blood in the form of urine. As long as this special regulation of fluid is maintained, the kidneys will make less urine in order to save fluid in instances where the amount of water intake is decreased, or water loss is increased (diarrhea, excessive sweating). Also, during night, the kidneys tend to produce less urine as a result of reduced rate of metabolism. Additionally, the hypothalamus produces a hormone known as Antidiuretic hormone (ADH) which stimulates the body to produce less amounts of urine at times.

A problem with the production of this antidiuretic hormone or aforementioned kidney’s response to an antidiuretic hormone is known to result in this condition known as Diabetes insipidus.

Patients affected by this condition will usually experience excessive urination and thirst associated with an increased fluid intake (preferably cold water or ice) In contrast to urine excreted in diabetes mellitus, urine in these patients will not contain glucose.

Some patients will also indicate signs of dehydration such as sunken eyes, dry mucous membranes, reduced skin turgor, etc. Untreated dehydration can result in Hypokalemia. Affected children may show loss of appetite and weight gain sometimes associated with fever, vomiting, or diarrhea.

Major investigations to diagnose this condition in clinically suspected patients include,

• Blood glucose levels
• Bicarbonate levels
• Calcium levels
• Serum electrolytes (hypernatremia and hypokalemia due to dehydration)
• Urinalysis (diluted urine with a low specific gravity)
• Fluid deprivation test (Distinguish DI from other causes of excessive urination) to see the etiology of diabetes insipidus which can either be due to a defect in ADH production or a defect in the kidneys’ response to ADH
• MRI and CT scans to identify defects in the pituitary gland and hypothalamus.

Treatment

Central and gestational Diabetes Insipidus are usually treated with Desmopressin which can be given intra-nasally or orally. Some patients will also respond to Carbamazepine (anticonvulsive drug).

It is also important to correct dehydration in affected individuals by using Hydrochlorothiazide (thiazide diuretic) or indomethacin.

Regulation of urine production by ADH and aldosterone

Difference Between Diabetes Mellitus and Diabetes Insipidus

Cause

Even though both these conditions have a common name and a symptom of producing more urine, their pathophysiology has a significant difference.

Diabetes mellitus is caused by a deficiency of the pancreatic hormone insulin.

Diabetes insipidus involves a problem with the production of antidiuretic hormone or kidney’s response to antidiuretic hormone (nephrogenic diabetes insipidus), 

Polyuria

Diabetes mellitus leads to polyuria by a process known as osmotic diuresis as a result of a leakage of high blood sugar levels into the urine.  

In diabetes insipidus, polyuria is caused by either a problem with the production of antidiuretic hormone or kidney’s response to antidiuretic hormone.

Glycosuria 

Glycosuria refers to the excess of sugar in the urine. 

Diabetes Insipidus doesn’t develop glycosuria like in Diabetes Mellitus.

Image Courtesy:

“Main symptoms of diabetes” By Mikael Häggström – (Public Domain) via Commons Wikimedia

“ADH3” By Rodrigo H. Castilhos – Own work (Public Domain) via Commons Wikimedia 

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