Encyclopedia of Health and Medicine

hyperkalemia 137
of the HEART’s rhythm (ARRHYTHMIA) that can have
serious consequences.
The most common cause of hyperaldosteronism
is an ADENOMA (a noncancerous tumor) that grows
in the zona glomerulosa, the region of the adrenal
cortex that produces aldosterone. Symptoms may
appear gradually or rapidly depending on the location
and rate of growth of the adenoma. In addition
to HYPERTENSION (high blood pressure) and arrhythmias,
symptoms may include HEADACHE and fatigue.
Some people also experience weakness or dizziness,
a potential consequence of arrhythmias.
The diagnostic path includes blood tests to
measure the levels of aldosterone and potassium,
imaging procedures such as COMPUTED TOMOGRAPHY
(CT) SCAN or MAGNETIC RESONANCE IMAGING (MRI) to
determine the presence of an adrenal tumor, and
ELECTROCARDIOGRAM (ECG) to detect and evaluate
any arrhythmias. Treatment is surgery to remove
the tumor, when possible. The endocrinologist
may also prescribe medications such as the potassium-sparing
diuretic spironolactone, which works
by suppressing aldosterone secretion, in conjunction
with a low-sodium diet to help control symptoms
either in lieu of surgery or after surgery if
the hypertension persists.
Hyperaldosteronism may also develop as a secondary
condition resulting from severe CARDIO-
VASCULAR DISEASE (CVD) such as uncontrolled
hypertension or HEART FAILURE. Treatment when
this is the case targets the underlying condition
and often also incorporates similar dietary restrictions
and medications to those prescribed for primary
hyperaldosteronism.
See also ADDISON’S DISEASE; ADRENAL INSUFFI-
CIENCY; CUSHING’S SYNDROME.
hypercalcemia A circumstance of excessive calcium
in the BLOOD circulation. The most common
cause of hypercalcemia is HYPERPARATHYROIDISM
(excessive secretion of PARATHYROID HORMONE).
Other causes include HYPERTHYROIDISM (overactive
THYROID GLAND), long-term therapy with lithium
(treatment for BIPOLAR DISORDER) or thiazide diuretics
(“water pills”), excessive vitamin D or vitamin
A consumption, excessive consumption of calcium
carbonate (a form of antacid often taken as a calcium
supplement), and some cancers, notably
metastatic BONE CANCER.
Hypercalcemia occurs when the bones release
excessive calcium into the BLOOD circulation. The
loss of calcium weakens the structure of the
bones, causing symptoms similar to OSTEOPOROSIS
such as BONE PAIN and, when calcium loss is severe,
spontaneous fractures. However, hypercalcemia is
likely to cause other, more apparent symptoms
before the calcium loss reaches such a point.
Calcium is essential for MUSCLE contractions and
for the conduction of NERVE impulses, an especially
critical combination in the HEART. Hypercalcemia
may cause ARRHYTHMIAS (irregularities in the
HEART RATE), which are apparent with ELECTROCAR-
DIOGRAM (ECG), and HYPERTENSION (high BLOOD PRES-
SURE). Hypercalcemia also often has neurologic
symptoms as well, such as confusion and cognitive
dysfunction, because the excessive calcium in the
blood disrupts nerve communication in the BRAIN.
The diagnostic path begins with blood tests to
measure calcium and parathyroid hormone levels
in the blood. The doctor may conduct an ECG to
evaluate any cardiovascular symptoms, and X-rays
Or bone scan to assess BONE DENSITY loss or the
presence of tumors, particularly in people who
have or have been treated for LYMPHOMA, LEUKEMIA,
MULTIPLE MYELOMA, or CARCINOMA. People who have
received RADIATION THERAPY to the neck, such as to
treat THYROID CANCER or HYPERTHYROIDISM, are vulnerable
to parathyroid ADENOMA (noncancerous
tumor of a parathyroid gland) or hyperparathyroidism.
Treatment depends on the severity of the
hypercalcemia and any underlying causes. Mild to
moderate hypercalcemia may improve with
increased HYDRATION in combination with medications
that suppress the release of calcium from the
bones or the diuretic medication furosemide
(Lasix), which blocks the KIDNEYS from reabsorbing
calcium from the blood. When the cause is hyperparathyroidism,
the most viable treatment option
may be surgery to remove the parathyroid glands.
When hypercalcemia results from benign causes,
treatment usually resolves the situation and blood
calcium levels return to normal.
See also CALCITONIN; MULTIPLE ENDOCRINE NEOPLA-
SIA (MEN); NEPHROLITHIASIS; PHEOCHROMOCYTOMA.
hyperkalemia A circumstance of elevated potassium
in the BLOOD circulation. The most common