Encyclopedia of Health and Medicine

hypopituitarism 143
or foods high in potassium such as bananas,
oranges, potatoes, and green leafy vegetables can
provide adequate potassium supplementation for
mild to moderate hypokalemia.
See also FANCONI’S SYNDROME; HYPERKALEMIA;
MEDICATIONS TO TREAT CARDIOVASCULAR DISEASE; RENAL
FAILURE.
hyponatremia A circumstance of insufficient
sodium in the BLOOD circulation. Hyponatremia is
a symptom of numerous underlying health conditions
rather than itself a disorder. The most common
cause of hyponatremia is DEHYDRATION,
typically as a consequence of extended VOMITING
and DIARRHEA or of diuretic therapy (medications
taken to reduce the volume of fluid in the body,
many of which work by causing the KIDNEYS to
increase the amount of sodium they pass from the
body in the URINE). Among the endocrine conditions
that cause hyponatremia are HYPOTHYROIDISM,
ADRENAL INSUFFICIENCY, ADDISON’S DISEASE, and
hypoaldosteronism. Nonendocrine systemic disorders
that can cause hyponatremia include
NEPHROTIC SYNDROME, RENAL FAILURE, CIRRHOSIS, LIVER
FAILURE, and congestive HEART FAILURE.
Mild hyponatremia may show no symptoms,
with the doctor making the detection during blood
tests done for various reasons to measure electrolyte
levels. Moderate to severe hyponatremia
has primarily neurologic symptoms, as the imbalance
between sodium and water in the BRAIN
affects communication among neurons (NERVE
cells). Symptoms include confusion, cognitive dysfunction,
and changes in mood or personality. The
diagnostic path typically includes blood tests to
measure the amounts of sodium and other electrolytes
in the blood, urinalysis to measure the
proportions of excreted electrolytes to water, and
appropriate tests and procedures to evaluate any
suspected endocrine or other health conditions
that could be responsible for the hyponatremia.
Hyponatremia requires prompt medical treatment
to restore the sodium balance in the blood
circulation. Often, identifying and targeting the
underlying cause (such as reducing the DOSE of a
diuretic medication or hormone supplementation
therapy to restore hormonal balance) brings about
homeostasis. Untreated hyponatremia can lead to
cerebral edema (swelling in the brain), loss of consciousness,
and death. When the cause is
endocrine dysfunction, such as hypothyroidism or
Addison’s disease, lifelong HORMONE THERAPY is typically
necessary. Many people fully recover from
hyponatremia though may need ongoing medical
treatment for the underlying health condition.
See also ALCOHOLISM; COGNITIVE FUNCTION AND
DYSFUNCTION; HYPERNATREMIA; MALNUTRITION; MEDICA-
TIONS TO TREAT CARDIOVASCULAR DISEASE.
hypoparathyroidism A rare condition in which
the amount of PARATHYROID HORMONE in the BLOOD
circulation is insufficient, as a consequence of
either dysfunction or absence of the PARATHYROID
GLANDS. Thyroidectomy (surgical removal of the
THYROID GLAND, such as to treat THYROID CANCER) is
the most common reason for absence of the
parathyroid glands, as the four parathyroid glands
rest on the back surface of the thyroid gland.
Occasionally the parathyroid glands are the target
of an autoimmune attack that destroys their ability
to function. Rarely, the parathyroid glands are
absent from birth, a congenital anomaly that
requires lifelong calcium and vitamin D supplement
therapy to maintain adequate blood calcium
levels as well as BONE STRENGTH and density.
Hypoparathyroidism results in inadequate calcium
(HYPOCALCEMIA) and excessive phosphorus
(hyperphosphatemia) in the blood. The symptoms
of hypoparathyroidism are those of hypocalcemia
and may include
• tingling of the toes, fingers, and lips
• MUSCLE cramps
• rarely, seizures
The diagnostic path includes blood tests to
measure the levels of calcium, phosphate, and
parathyroid hormone in the blood circulation.
Treatment for confirmed hypoparathyroidism is
supplementation with calcium and vitamin D.
When the parathyroid glands are missing or
destroyed, lifelong treatment is necessary.
See also HYPERCALCEMIA; HYPERPARATHYROIDISM;
MINERALS AND HEALTH; OSTEOPOROSIS; VITAMINS AND
HEALTH.
hypopituitarism A condition in which the PITU-
ITARY GLAND secretes an insufficient amount of one