Encyclopedia of Health and Medicine

142 The Endocrine System
though some people may experience symptoms of
hypoglycemia with blood glucose levels between
50 mg/dL and 70 mg/dL.
Hypoglycemia most commonly occurs in people
who have DIABETES, manifesting as a consequence
of taking more INSULIN or antidiabetes medication
than is necessary to balance carbohydrate consumption
or due to a more intense level of physical
activity than usual, which increases the body’s
need for glucose. Hypoglycemia also can occur in
people who do not have diabetes, often as a result
of inadequate carbohydrate consumption particularly
during intense physical exercise or with
extended fasting (going without food). Excessive
ALCOHOL consumption, particularly in people who
have CIRRHOSIS of ALCOHOLISM or other LIVER disease,
may also cause hypoglycemia. An uncommon
form of nondiabetes hypoglycemia is reactive
hypoglycemia, in which the blood glucose level
drops within three to four hours after eating.
Researchers do not know what causes reactive
hypoglycemia.
Imbalances or dysfunctions of the endocrine
system’s hormonal cascades may slow the body’s
efforts to restore adequate blood glucose levels. In
health, a low blood glucose level triggers the ISLETS
OF LANGERHANS to release GLUCAGON, which directs
the liver to convert glycogen (a storage form of
glucose) to glucose. Simultaneously, the HYPOTHAL-
AMUS releases CORTICOTROPIN-RELEASING HORMONE
(CRH) and GROWTH HORMONE–RELEASING HORMONE
(GHRH), which set in motion hormonal cascades to
alter METABOLISM in ways that slow the body’s use
of glucose.
The symptoms of hypoglycemia include
• feeling weak and shaky
• hunger
• excessive sweating
• drowsiness and confusion
• acting intoxicated
• dizziness and lightheadedness
People who have diabetes should check their
blood glucose levels at the onset of any of these
symptoms. Immediate treatment generally
resolves the symptoms, and may include drinking
a glass of juice or soda (regular, not diet or sugarfree
products), eating a spoonful of sugar or
honey, or eating a small amount of candy. The
doctor may follow up with diagnostic tests to
determine the cause of the hypoglycemic episode,
such as blood tests to measure glucose levels during
symptoms. The body’s needs for insulin and
glucose vary with physical activity, so people who
have diabetes may need to adjust their medication
doses if they increase their exercise levels and
experience repeated episodes of hypoglycemia.
Eating small meals frequently (every three hours)
maintains a more consistent level of glucose in the
blood circulation and is the therapeutic approach
doctors recommend for people who have reactive
hypoglycemia. Though untreated hypoglycemia
can have significant consequences including coma
and death, most people respond quickly to treatment
and recover without residual effects.
See also INSULIN RESISTANCE.
hypokalemia A circumstance of low potassium
in the BLOOD circulation. There are many causes of
hypokalemia. Among the most common are persistent
DIARRHEA (which depletes electrolytes from
the body), long-term therapy with diuretic medications
(many of which cause the KIDNEYS to
excrete potassium), and kidney disease (which
affects the ability of the kidneys to regulate potassium
retention). Endocrine causes for
hypokalemia include HYPERALDOSTERONISM (oversecretion
of ALDOSTERONE) and excessive ADRENO-
CORTICOTROPIN HORMONE (ACTH) such as occurs with
CUSHING’S SYNDROME.
The symptoms of hypokalemia are those of
electrolyte imbalance. Mild to moderate symptoms
may include MUSCLE weakness or cramping,
fatigue, and excessive thirst. Significant hypokalemia
can cause confusion, disorientation, and
ARRHYTHMIA (irregular heartbeat). Without treatment
hypokalemia has the potential to be fatal as
it can result in HEART ATTACK or PARALYSIS of the
muscles that impairs BREATHING.
The diagnostic path begins with blood tests that
measure the levels of potassium, sodium, magnesium,
and other electrolytes in the blood. An ELEC-
TROCARDIOGRAM (ECG) identifies any arrhythmias.
Treatment is potassium supplementation, which
may need to be intravenous when symptoms are
severe. Potassium tablets (as the doctor prescribes)