|
Diabetes Insipidus Fact Book
|
|
dibetes, diabets, diabetis, insipidas
Introduction
|
Diabetes insipidus (DI) is characterized by excretion of large amounts
of dilute urine, which disrupts your body's water regulation. To make up
for lost water, you may feel the need to drink large amounts of water. You
are likely to urinate frequently, even at night, which can disrupt sleep
or, on occasion, cause bedwetting. Because of the excretion of abnormally
large volumes of dilute urine, you may quickly become dehydrated if you do
not drink enough water. Children with DI may be irritable or listless and,
in some cases, may have fever, vomiting, or diarrhea.
|
|
Your body has a complex system for balancing the volume and composition
of body fluids. Your kidneys remove extra body fluids from your
bloodstream. This fluid waste is stored in the bladder as urine. If your
fluid regulation system is working properly, your kidneys make less urine
to conserve fluid when the body is losing water. Your kidneys also make
less urine at night when the body's metabolic processes are slower.
The hypothalamus makes antidiuretic hormone (ADH), which
directs the kidneys to make less urine.
|
In order to keep the volume and composition of body fluids balanced,
the rate of fluid intake is governed by thirst, and the rate of excretion
is governed by the production of antidiuretic hormone (ADH), also called
vasopressin. This hormone is made in the hypothalamus, a small gland
located in the base of the brain. ADH is stored in the nearby pituitary
gland and released from it into the bloodstream when necessary. When ADH
reaches the kidneys, it directs the kidneys to concentrate the urine by
returning excess water to the bloodstream and therefore make less urine.
DI occurs when this precise system for regulating the kidneys' handling
of fluids is disrupted. The most common form of DI, central DI, results
from damage to the pituitary gland, which disrupts the normal storage and
release of ADH. Another form, nephrogenic DI, results when the kidneys are
unable to respond to ADH. Rarer forms occur because of a defect in the
thirst mechanism (dipsogenic DI) or during pregnancy (gestational DI).
|
|
DI should not be confused with diabetes mellitus, which results from
insulin deficiency or resistance. Diabetes insipidus and diabetes mellitus
are unrelated, although they can have similar signs and symptoms, like
excessive thirst and excessive urination.
Diabetes mellitus (DM) is far more common than DI and receives more
news coverage. DM has two forms, referred to as type 1 diabetes (formerly
called juvenile diabetes, or insulin-dependent diabetes mellitus, or IDDM)
and type 2 diabetes (formerly called adult-onset diabetes, or
noninsulin-dependent diabetes mellitus, or NIDDM). DI is a different form
of illness altogether.
|
|
Damage to the pituitary gland can be caused by different diseases as
well as by head injuries, neurosurgery, or genetic disorders. To treat the
resulting ADH deficiency, a synthetic hormone called desmopressin can be
taken by an injection, a nasal spray, or a pill. While taking
desmopressin, you should drink fluids or water only when you are thirsty
and not at other times. This is because the drug prevents water excretion
and water can build up now that your kidneys are making less urine and are
less responsive to changes in body fluids.
|
|
The kidneys' ability to respond to ADH can be impaired by drugs (like
lithium, for example) and by chronic disorders including polycystic kidney
disease, sickle cell disease, kidney failure, partial blockage of the
ureters, and inherited genetic disorders. Sometimes the cause of
nephrogenic DI is never discovered.
Desmopressin will not work for this form of DI. Instead, you may be
given a drug called hydrochlorothiazide (also called HCTZ) or
indomethacin. HCTZ is sometimes combined with amiloride. Again, you should
drink fluids only when you are thirsty and not at other times.
|
|
A third type of DI is caused by a defect in or damage to the thirst
mechanism, which is located in the hypothalamus. This defect results in an
abnormal increase in thirst and fluid intake that suppresses ADH secretion
and increases urine output. Desmopressin or other drugs should not be used
to treat dipsogenic DI because they may decrease urine output but not
thirst and fluid intake. This fluid "overload" can lead to water
intoxication, a condition that lowers the concentration of sodium in the
blood and can seriously damage the brain.
|
|
A fourth type of DI occurs only during pregnancy. Gestational DI occurs
when an enzyme made by the placenta destroys ADH in the mother. The
placenta is the system of blood vessels and other tissue that develops
with the fetus. The placenta allows exchange of nutrients and waste
products between mother and fetus.
Most cases of gestational DI can be treated with desmopressin. In rare
cases, however, an abnormality in the thirst mechanism causes gestational
DI, and desmopressin should not be used.
A specialist should determine which form of DI is present before
starting any treatment.
|
|
Because DM is more common and because DM and DI have similar symptoms,
a health care provider may suspect that a patient with DI has DM. But
testing should make the diagnosis clear.
Your physician must determine which type of DI is involved before
proper treatment can begin. Diagnosis is based on a series of tests,
including urinalysis and a fluid deprivation test.
Urinalysis is the physical and chemical examination of urine. The urine
of a person with DI will be less concentrated. Therefore, the salt and
waste concentrations are low, and the amount of water excreted is high. A
physician evaluates the concentration of urine by testing its specific
gravity or osmolality.
A fluid deprivation test helps determine whether DI is caused by (1)
excessive intake of fluid, (2) a defect in ADH production, or (3) a defect
in the kidneys' response to ADH. This test measures changes in body
weight, urine output, and urine composition when fluids are withheld.
Sometimes measuring blood levels of ADH during this test is also
necessary.
In some patients, an MRI (magnetic resonance imaging) of the brain may
be necessary as well.
Keeping on Top of Your Condition
Keeping in tune with your disease or condition not only makes treatment less intimidating but also increases its chance of success, and has been shown to lower a patients risk of complications. As well, as an informed patient, you are better able to discuss your condition and treatment options with your physician.
A new service available to patients provides a convenient means of staying informed, and ensures that the information is both reliable and accurate. If you wish to find out more about HealthNewsflash's innovative service, take the tour.
|
|
For more information, contact the following organizations:
The Diabetes Insipidus Foundation, Inc.
4533 Ridge Drive
Baltimore, MD 21229
Phone: (410) 247-3953
Email: diabetesinsipidus@maxinter.net
Internet: diabetesinsipidus.maxinter.net
The Diabetes Insipidus and Related Disorders Network
535 Echo
Court
Saline, MI 48176-1270
Phone: (734) 944-0078
Email: gsmayes@aol.com
Internet: hometown.aol.com/ruudh/dipage1.htm
National Organization for Rare Disorders Inc. (NORD)
55
Kenosia Avenue
P.O. Box 1968
Danbury, CT 06813-1968
Phone:
1-800-999-6673 or (203) 744-0100
Fax: (203) 798-2291
Email: orphan@rarediseases.org
Internet:
http://www.rarediseases.org/
Nephrogenic Diabetes Insipidus Foundation
Main Street
P.O.
Box 1390
Eastsound, WA 98245
Phone: 1-888-376-6343
Fax:
1-888-376-3842
Email: info@ndif.org
Internet: http://www.ndif.org/
|
|
|
|
