What is the difference between diabetes mellitus and diabetes insipidus?

The word diabetes is an interesting one. Its origin is in the Greek language where it is derived from the word for a siphon or, more simply, a pipe or hose. This word was used to describe the disorder in ancient times (and diabetes was recognized in great antiquity) because those suffering from it produced such plentiful amounts of urine that they were reminiscent of a water pipe. The reason for the plentiful amounts of urine lies in the fact that when the sugar glucose reaches excessively high levels in our bloodstream, it is filtered into the kidney and enters the urine in large quantities. Due to its chemical and physical properties, when large amounts of glucose are filtered by our kidneys into the urine, it cannot be fully reabsorbed and retains a large amount of water with it, thus creating very large volumes of urine. The second part of the name, mellitus, is derived from the word meaning sweet, as in mellifluous music. Mellitus was added when it was discovered that the urine in a person with diabetes and very high blood sugar is sweet.

Diabetes insipidus is a disorder with an entirely different basis, but its sufferers share the siphon-like quality of very frequent and very high volume urination. Diabetes insipidus is due to failure of production or action of another vital hormone, known as arginine vasopressin (AVP), also called antidiuretic hormone (ADH), that is responsible for maintaining the normal volume and concentration of our urine. When AVP is deficient (usually due to damage or disease of the hypothalamus or pituitary gland) or fails to work (usually due to disease of or damage to the kidney), we are unable to concentrate our urine and it becomes excessively dilute. As such, it appears pale, almost colorless and watery — in a word insipid, hence insipidus. It is not sweet, as it has negligible amounts of sugar in it.

Diabetes mellitus

A condition characterized by inadequate production of insulin or resistance of the body's tissues toits actions, which results In excessive levels of glucose In the blood.

Diabetes Insipidus

Increased urine production caused by Inadequate secretion of vasopressin by the pituitary gland or by resistance of the kidney to Its actions.

Arginine vasopressin (AVP)

A hormone that Is responsible for maintaining the normal volume and concentration of our urine. Also called antidiuretic hormone (ADH).

What are the symptoms of diabetes?

The typical symptoms of diabetes occur as a result of the high levels of glucose in the bloodstream and its passage into the urine and other tissues. These are frequent urination and thirst. Thirst arises as a result of the dehydration caused by the frequent urination. Dehydration and loss of nutrient calories in the urine lead to weight loss and hunger. Passage of glucose into the tissues of the eye can cause fluctuating degrees of blurred vision.

Antidiuretic hormone (ADH)

A hormone that is responsible for maintaining the normal volume and concentration of our urine. Also called arginine vasopressin (AVP).

One of every four people believed to have diabetes is unaware of it and is undiagnosed.

Neuropathy

Nerve damage.

Prediabetes

A condition in which abnormalities in plasma glucose levels lie in-between normal and standard accepted definitions of diabetes. "Borderline diabetes," "impaired fasting glucose," and "impaired glucose tolerance" are other terms used to describe types of this condition.

Retinopathy

Eye damage.

Nephropathy

Kidney damage.

When these symptoms are prolonged and severe, as is typical with type 1 diabetes, serious changes occur in our blood chemistry due to the deficiency of insulin. Those changes, coupled with dehydration, result in dizziness, weakness, drowsiness, and ultimately coma, which if untreated can lead to death. Both type 1 and type 2 diabetes, when severe and inadequately treated, can be associated with coma and death. Although coma is less common in type 2 diabetes, it is more common for it to result in death, as people with type 2 diabetes tend to be older and to have more medical problems. Two other important points are worth noting. The first is that diabetes may not cause any symptoms. In fact, one of every four people believed to have diabetes is unaware of it and is undiagnosed. However, as diabetes of even moderate severity can lead to complications and shorten lifespan, it is important to make the diagnosis, even in people without symptoms. The second point is that the majority of people with diabetes may not have any symptoms from the elevated blood sugar, but it can still present with symptoms from its complications. Thus, people may be diagnosed with diabetes after presenting with symptoms of nerve damage (neuropathy — see Question 32) or a heart attack or stroke (see Question 35). In fact, one of every three people admitted with a sudden heart event is found to have diabetes or prediabetes (see Question 9) of which he or she or the doctor was unaware. Neuropathy is present in two of every five patients with type 2 diabetes at the time of diagnosis, while eye damage (retinopathy — see Question 33) is present in one of every five and kidney damage (nephropathy — see Question 34) is present in one in ten, indicating that the diabetes was ongoing for many months or even years before diagnosis.

 
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