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Diabetes Insipidus: How Is It Different From Diabetes Mellitus?

urinary incontinence

Diabetes insipidus should not be confused with diabetes mellitus.  Although they may both have similar signs and symptoms (such as excessive thirst and urination), they are unrelated conditions.

Diabetes mellitus (commonly referred to as simply "diabetes") is a far more common condition.  It is caused by insulin deficiency or insulin resistance, leading to high blood glucose levels.  Diabetes mellitus (DM) is classified into two categories: Type I and Type 2.

Basically, with type 1 the body either stops producing insulin or does not produce enough.

With type 2 diabetes, the body does not respond as it should to insulin... Hence the reason it is sometimes referred to as an insulin-resistant condition.

Diabetes insipidus is a completely different condition.  It is not caused by an insulin deficiency or insulin resistance problem.

Diabetes Insipidus Overview

The body has a rather complex system for balancing and regulating the volume and composition of its fluids.  The process actually starts in the brain and ends with the urinary system.

Within the urinary system, the kidneys are responsible for removing excess fluids from the blood stream, where it is transformed into urine, stored in the bladder and eventually expelled from the body when we urinate.  Under normal conditions, the kidneys' production of urine is proportional to the volume of fluids consumed and the volume of fluids needed by the body.  For instance, if you drink large amounts of fluids over a short period of time your kidneys should produce more urine, to get rid of excess fluids. On the other hand, if your fluid consumption is low, the kidneys should produce less urine, in order to conserve fluids in the body.

When the body's fluid-regulating system is disrupted or malfunctions, diabetes insipidus occurs.  It affects the balance between the amount of fluid that remains in the body and the amount excreted as urine.  In other words, the volume and composition (or concentration) of fluids within the body are thrown out of balance.

What Causes Diabetes Insipidus?

A hormone called antidiuretic hormone (ADH), also called vasopressin, is responsible for regulating the volume of fluids excreted or removed by the kidneys.  ADH is produced by the hypothalamus (a small gland located at the base of the brain) and stored in the pituitary gland (also located in the brain).

Basically, this hormone tells the kidneys how much fluid should be removed from the blood and converted to urine.  ADH or vasopressin ensures that sufficient fluids remain in the body to avoid dehydration and to facilitate metabolism and other essential biochemical functions.  Without this hormone, the kidneys tend to extract more fluids from the body than they should.

Diabetes Insipidus occurs when the storage or release of this vital hormone is affected, or if the kidneys are unable to respond to it as they should.  This can occur when, for instance, there is damage to the pituitary gland or to the kidneys, which affect their ability to respond to ADH.

Another cause is damage to, or a defect of, the thirst mechanism located in the hypothalamus.  This results in abnormal increase in thirst and fluid consumption, which suppresses the secretion of the vasopressin hormone and increases urine output.

Symptoms Of Diabetes Insipidus

The symptoms of Diabetes Insipidus are very similar to diabetes mellitus. The most common symptoms include:

  • Passing large amounts of urination;

  • Clear, colorless urine;

  • Excessive thirst;

  • Dehydration.

How Is It Treated

Treatment usually involves medication or replacement hormone. If for instance the pituitary gland is damaged, resulting in ADH deficiency, a synthetic hormone (called desmopressin) may be administered.

If the cause is the kidneys' inability to respond to ADH, other drugs (such as indomethacin) may be required.  Patients may also be required to balance their fluid intake, to control some symptoms such as excessive urination.

If, over a period of time, you notice that you are always thirsty and your urine is clear and its volume is unusually large, please check with your doctor. These may be signs and symptoms of diabetes insipidus.

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