Webster's New World Medical Dictionary

hypotension, orthostatic
A temporary lowering
of blood pressure, usually related to suddenly
standing up. Healthy people may experience ortho-
static hypotension if they rise quickly from a seated
position, especially after a meal. Orthostatic
hypotension occurs most commonly in older peo-
ple. The change in position causes a temporary
reduction in blood flow and therefore a shortage of
oxygen to the brain. This leads to lightheadedness,
dizziness, and, sometimes, a temporary loss of con-
sciousness. Tilt-table testing can be used to confirm
a diagnosis of orthostatic hypotension. Tilt-table
testing involves placing the patient on a table with a
foot support. The table is tilted upward, and blood
pressure and pulse are measured while symptoms
are recorded in various positions. Also known as
postural hypotension.
hypotension, postural
See 
hypotension, ortho-
static.
hypothalamus
The area of the brain that
secretes substances that influence pituitary and
hypomania
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other gland function and is involved in the control
of body temperature, hunger, thirst, and other
processes that regulate body equilibrium.
hypothermia
Abnormally low body temperature.
Someone who falls asleep in a cold temperature
may become hypothermic, and the condition can be
fatal. Hypothermia is intentionally produced to slow
the metabolism during some types of surgery. Severe
hypothermia can be fatal. Those with mild or mod-
erate hypothermia (are alert and conscious, and
have not lost the shivering reflex) will usually sim-
ply require removing them from the cold environ-
ment and providing them with additional insulation.
Treatment of severe hypothermia involves slow heat-
ing of the body using blankets or other ways of
increasing body warmth. Body temperature should
increase by no more than a couple of degrees per
hour.
hypothyroid
Deficiency of thyroid hormone. The
hypothyroid state (hypothyroidism) is characterized
by fatigue, weight gain, and constipation. Severe,
longstanding hypothyroidism can lead to swelling of
the extremities, coma, and death.