Aldosterone also acts on the peripheral arterioles,
the tiny arteries within the tissues, causing them
to constrict. The combined effect of increased
blood volume and peripheral vasoconstriction
causes blood pressure to rise. This is a funda-
mental cascade of one of the body’s primary
blood pressure–regulatory mechanisms, the renin–
angiotensin–aldosterone (RAA) system. Some
medications to treat congestive HEART FAILUREand
HYPERTENSION(high blood pressure) work by block-
ing the action of aldosterone.
Aldosterone deficiency, such as may result with
ADRENAL INSUFFICIENCY and ADDISON’S DISEASE,
causes HYPOTENSION(low blood pressure) and elec-
trolyte imbalances that can cause ARRHYTHMIA(dis-
turbance of the HEART’s rhythm and rate).
Untreated aldosterone deficiency is fatal. Treat-
ment with hormone-replacement therapy restores
homeostasis. Excessive aldosterone in the blood-
stream (HYPERALDOSTERONISM) typically results from
an adrenal ADENOMA(noncancerous tumor) arising
from the middle section of the adrenal cortex, the
zona fasciculata, which produces aldosterone.
For further discussion of aldosterone within the
context of the endocrine system’s structure and
function please see the overview section “The
Endocrine System.”
See also ADRENOCORTICOTROPIC HORMONE(ACTH);
CORTICOTROPIN-RELEASING HORMONE(CRH); CORTISOL;
DOPAMINE; EPINEPHRINE; NOREPINEPHRINE.
amyloidosis An uncommon and potentially fatal
disorder of METABOLISMin which the BONE MARROW
produces defective antibodies that result in an
abnormal protein, amyloid. The amyloid leaves
the bone marrow in the BLOODand forms fibrous
deposits in organs and tissues throughout the
body. The deposits interfere with normal func-
tions, which can result in severe damage to and
failure of organs such as the HEART, LIVER, and KID-
NEYS. Amyloid deposits can also accumulate in the
nerves and NERVOUS SYSTEM, LYMPH NODES, and
blood vessels. There are three forms of amyloido-
sis: primary, secondary, and hereditary.
Primary amyloidosis Primary amyloidosis, also
called idiopathic amyloidosis, occurs independ-
ently of other disease processes and without
known cause (idiopathic). Most people who have
amyloidosis have this form, which tends to affect
the heart, LUNGS, THYROID GLAND, liver, intestines,
SKIN, and tongue.
Secondary amyloidosis Secondary amyloidosis
accompanies or occurs as a consequence of other
disease processes. The most common association is
with MULTIPLE MYELOMA, a CANCERof the lymph sys-
tem. About 15 percent of people who have multi-
ple myeloma develop secondary amyloidosis.
Secondary amyloidosis also may occur in conjunc-
tion with chronic inflammatory disorders such as
RHEUMATOID ARTHRITIS or with chronic INFECTION
such as TUBERCULOSISand OSTEOMYELITIS. Secondary
amyloidosis tends to affect the liver, SPLEEN, kid-
neys, ADRENAL GLANDS, and lymph nodes.
Hereditary amyloidosis Rarely, a person inher-
its amyloidosis as a result of geneticMUTATION. The
amyloid deposits in hereditary amyloidosis are
most likely to accumulate in the heart, kidneys,
intestines, vitreous humor (the gelatinous sub-
stance inside the EYE), and PERIPHERAL NERVES.Symptoms and Diagnostic Path
Symptoms of amyloidosis vary, depending on the
organ systems affected. Many people experience
generalized symptoms such as weakness, tiredness
and fatigue, and unexplained weight loss. Other
symptoms that may occur with amyloid deposits
in specific organs or systems include- DIARRHEA(gastrointestinal)
- tingling and numbness in the hands and feet
(nerves) - ARRHYTHMIA (irregularities in the heartbeat;
heart) - swollen tongue and difficulty swallowing
(tongue; gastrointestinal; nerves) - DYSPNEA(shortness of breath; lungs, heart)
- HEPATOMEGALY(enlarged liver; liver)
Amyloidosis also may manifest through symp-
toms of disease process such as HYPOTHYROIDISM
(amyloid deposits in the thyroid gland) and kid-
ney failure (amyloid deposits in the kidneys). The
diagnostic path includes clinical assessment of
symptoms, blood and URINEtests that may detect112 The Endocrine System