Diabetes Insipidus
A disorder of the posterior pituitary, diabetes insipidus is caused by
a deficiency of antidiuretic hormone (ADH). Antidiuretic hormone is secreted
in response to serum osmolality, which is monitored by osmoreceptors in the
hypothalamus. Hypo-osmolality, an increase in the volume of fluid in the
body, causes the suppression of ADH which leads to an increase in the amount
of urine excreted everyday.
There are two types of diabetes insipidus:
1. Neurogenic diabetes insipidus - This form of the disease can result from
either a disruption of the hypothalamus and pituitary gland. This can be
caused by trauma, radiation therapy, or cranial surgery or an unknown cause.
2. Nephrogenic diabetes insipidus – This is a disorder of the renal tubules
in the kidneys are not sensitive to the effects of ADH. This can have
genetic causes or happen as a result of renal failure.
Diabetes insipidus may be a result of any number of reasons including brain
tumors of infections, cerebral vascular accidents, pituitary surgery, and
renal or organ failure. Increased intracranial pressure due to a closed head
trauma can also lead to complications of diabetes insipidus.
A large amount of dilute urine, known as polyuria, is the primary
complication of insufficient ADH. In fact some people may void as much as 12
liters per day. People suffering from this disease will also exhibit extreme
thirst and will drink large amounts of water throughout the day. Even with
drinking large volumes of water the person who suffers from this may not be
able to replace the water they are losing. This can lead to dehydration and
hypernatremia, which is a deficit of water leading to an elevated sodium
level.
If the diabetes insipidus is caused by a cerebral injury the symptoms will
usually appear around 3 to 6 days after the injury happened and the symptoms
will last for 7 to 10 days. If it is being cause by an increase in
intracranial pressure relief of the pressure will normally cause the
symptoms to disappear. Diabetes insipidus can also be a chronic condition
that will need to be treated for the life of the patient.
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