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 BLOODcirculation. Hyponatremia is
a symptom of numerous underlying health condi-
tions rather than itself a disorder. The most com-
mon cause of hyponatremia is DEHYDRATION,
typically as a consequence of extended VOMITING
and DIARRHEAor of diuretic therapy (medications
taken to reduce the volume of fluid in the body,
many of which work by causing the KIDNEYSto
increase the amount of sodium they pass from the
body in the URINE). Among the endocrine condi-
tions that cause hyponatremia are HYPOTHYROIDISM,
ADRENAL INSUFFICIENCY, ADDISON’S DISEASE, and
hypoaldosteronism. Nonendocrine systemic disor-
ders 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 elec-
trolyte levels. Moderate to severe hyponatremia
has primarily neurologic symptoms, as the imbal-
ance between sodium and water in the BRAIN
affects communication among neurons (NERVE
cells). Symptoms include confusion, cognitive dys-
function, and changes in mood or personality. The
diagnostic path typically includes blood tests to
measure the amounts of sodium and other elec-
trolytes 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 treat-
ment to restore the sodium balance in the blood
circulation. Often, identifying and targeting the
underlying cause (such as reducing the DOSEof 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 con-
sciousness, and death. When the cause is
endocrine dysfunction, such as hypothyroidism or
Addison’s disease, lifelong HORMONE THERAPYis typ-
ically 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 HORMONEin 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 abil-
ity to function. Rarely, the parathyroid glands are
absent from birth, a congenital anomaly that
requires lifelong calcium and vitamin D supple-
ment therapy to maintain adequate blood calcium
levels as well as BONE STRENGTHand density.
Hypoparathyroidism results in inadequate cal-
cium (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
- MUSCLEcramps
- 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 GLANDsecretes an insufficient amount of onehypopituitarism 143