What has been called “type 3 diabetes”?
The term “type 3 diabetes” was introduced around 2005 as another name proposed for Alzheimer’s disease. This was suggested because of the possible connection between insulin resistance in the brain and the eventual onset of Alzheimer’s. Other recent studies indicate that Alzheimer’s is accompanied by inflammation, or the body’s response to an invading microbe (in fact, postmortem studies commonly reveal microbes in the brains of the elderly). Perhaps one day researchers will discover that inflammation and diabetes may be two of the major conditions that lead to the development of Alzheimer’s, especially since a person with type 1 or type 2 diabetes often has difficulty fighting off inflammation. But at this writing, the true reason(s) for Alzheimer’s is still highly debated.
What is Alzheimer’s disease?
Alzheimer’s disease occurs when there are nerve-cell changes in certain parts of the brain. These changes result in the death of a large number of cells, causing several symptoms that range from mild forgetfulness to serious impairments in thinking, judgment, and the ability to perform daily activities.
What is diabetes insipidus?
Diabetes insipidus (DI) is not a true form of diabetes but rather a rare disease linked to the body’s hypothalamus and pituitary gland. Similar in some symptoms to diabetes mellitus (DM), DI causes frequent urination and excessive thirst, but that is where the similarities end. Diabetes mellitus is associated with the body’s pancreas and is caused by insulin deficiency or resistance, thus leading to an imbalance in blood glucose (sugar) levels. On the other hand, DI occurs when the system that regulates the kidney’s handling of fluids is upset by certain circumstances, such as disease or trauma.
What steps lead to developing diabetes insipidus?
Diabetes insipidus occurs when the body’s fluids become unbalanced. Normally, the body balances fluid volume and composition, with the fluid intake governed by thirst and the rate of excreting urine by the production of vasopressin, also called antidiuretic hormone (ADH). This hormone is made in a small gland in the brain called the hypothalamus. The ADH is then stored in the nearby pituitary gland and released when needed into the bloodstream. When the ADH reaches the kidneys, it concentrates urine by reabsorbing some of the filtered water into the bloodstream, therefore making less urine. When this system is not working properly—in other words, when the kidneys’ ability to regulate fluids does not work well—the result is often DI.
How does a doctor test for diabetes insipidus?
Because diabetes insipidus and diabetes mellitus have a crossover of symptoms—chiefly frequent urination and excessive thirst—a health care provider may suspect that a person with DI actually has diabetes mellitus. Therefore, testing is needed to distinguish the difference, including urinalysis (to determine the concentration of a person’s urine) and a fluid-deprivation test (which will change body weight, urine output, and urine concentration when fluids are withheld, all of which can be used to learn whether there is any defect in ADH production or the kidneys’ response to ADH).
What are the various forms of diabetes insipidus (DI)?
There are several different forms of diabetes insipidus. The following lists some of these forms and the factors that explain the differences:
• Central DI—This is the most common form of DI. It is caused by damage to the pituitary gland, which stops the normal storage and release of ADH (antidiuretic hormone). Damages to the pituitary gland can be caused by a variety of diseases, head injuries, neurosurgery, or even genetic disorders.
• Nephrogenic DI—This is caused by a disruption in the kidneys’ ability to respond to ADH. The disruption can be caused by various drugs (lithium, for example) or by several types of chronic diseases, such as sickle-cell disease, inherited genetic disorders, kidney failure, or partial blockage of the ureters. It is often treated with several drugs, including hydrochlorothiazide.
• Dipsogenic DI—This is caused by an actual defect in or damage to the body’s thirst mechanism, which is located in the brain’s hypothalamus. Abnormal increase in thirst and fluid intake are seen in a person with this problem, and those, in turn, suppress ADH secretion—and increase the urine output. So far, there is no real treatment for dipsogenic DI. (For more about ureters and the urinary system, see the chapter “How Diabetes Affects the Urinary System.”)
• Gestational DI—Similar to gestational diabetes, gestational DI occurs only during pregnancy, but that is where the similarity ends. Gestational DI results when a specific enzyme made by the placenta destroys the ADH in the mother. (The placenta is the system of tissues and blood vessels that develop with the fetus; it is attached to the mother, supplying nutrients and eliminating waste products between the fetus and mother.) It is most often treated with desmopressin (although there is a rare form of gestational DI, in which the thirst mechanism is abnormal, which is not treated with desmopressin).
What is “uric acid diabetes”?
According to a recent study, there may be a connection between uric acid and how the body metabolizes carbohydrates and fats (lipids). The researchers suggested the phrase “uric acid diabetes” after discovering a statistically high incidence of diabetes in people with hyperuricemia (an abnormally high amount of uric acid in the blood), gout, or both. But more studies need to be conducted to verify whether there truly is a uric acid–diabetes connection. (For more about uric acid, see the chapter “How Diabetes Affects the Urinary System.”)