Webster's New World Medical Dictionary

diabetes insipidus
A metabolic disorder that
mimics symptoms of diabetes mellitus, including
increased output of urine and increased thirst. It is
caused by a malfunction in the pituitary gland, and
can be treated by administering vasopressin, a pitu-
itary hormone. There are two types of diabetes
insipidus, central and nephrogenic. Central diabetes
insipidus is a lack of ADH production and is due to
damage to the pituitary gland or hypothalamus where
ADH is produced. Nephrogenic diabetes insipidus is
a lack of response of the kidney to the fluid-conserv-
ing action of ADH. It can be due to diseases of the
kidney (such as polycystic kidney disease), certain
drugs (such as lithium), and can also occur as an
inherited disorder. The main danger is when fluid
intake does not keep pace with urine output, result-
ing in dehydration and high blood sodium. The treat-
ment of central diabetes insipidus is with vasopressin.
Nephrogenic diabetes insipidus does not respond to
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vasopressin treatment. In cases of nephrogenic dia-
betes insipidus caused by a drug (such as lithium),
stopping the drug usually leads to recovery. In cases
of hereditary nephrogenic diabetes insipidus, treat-
ment is with fluid intake to match urine output and
drugs that lower urine output. See also 
antidiuretic
hormone; pituitary, posterior.
diabetes mellitus
A chronic condition associ-
ated with abnormally high levels of sugar (glucose)
in the blood and urine. Absence of, insufficient pro-
duction of, or autoimmune resistance to the pan-
creatic hormone insulin causes diabetes. Insulin
provides the body with a natural method for oxidiz-
ing glucose to provide energy; without enough
insulin, glucose builds up in the bloodstream to
dangerous levels. The tendency to develop diabetes
runs in families, but not all patients have such a
family history. Symptoms of diabetes include
increased urine output, increased appetite and
thirst, unexplained weight loss or fluctuation, and
fatigue. Diabetes mellitus is diagnosed through
blood sugar testing. Major complications include
dangerously elevated blood sugar levels, abnormally
low blood sugar levels due to incorrect dosing of
diabetes medications, and disease of the blood ves-
sels, which can damage the eyes, kidneys, nerves,
and heart. Circulation problems due to blood vessel
damage may also endanger the patient’s feet and
legs. When the body cannot use glucose for energy
because of inadequate insulin in diabetes, it turns to
burning fat as energy. This process creates com-
pounds called ketones. If the blood level of ketones
gets too high, the result is a dangerous condition
called ketosis that, if unchecked, can cause lethargy,
convulsions, coma, and death. Treatment depends
on the type of diabetes. Diet is always the primary
treatment. Many patients take medications that help
to regulate their production and use of insulin.
Others may need insulin injections, either self-
administered via syringe or, more recently, via an
almost-painless “gun” device, an external insulin
pump, or an internally implanted insulin pump.
There are two forms of diabetes mellitus, type 1
(insulin requiring) and type 2 (non-insulin requir-
ing). Approximately 10 percent of the patients with
diabetes mellitus have type 1 diabetes; the remain-
ing 90 percent have type 2 diabetes mellitus.
Diabetes mellitus is commonly referred to as dia-
betes, though technically there are two forms of dia-
betes, diabetes mellitus and diabetes insipidus,
which are distinctly different conditions, both of
which are characterized by the excessive production
of dilute urine. See also 
diabetes, type 1; diabetes,
type 2.