the blood may remain artificially high in HYPOTHY-
ROIDISM, as the levels of thyroid hormones are
chronically inadequate in this condition of under-
active thyroid gland. TSH levels may be normal or
low in HYPERTHYROIDISM(overactive thyroid gland),
depending on the cause of the oversecretion of
thyroid hormones.
For further discussion of TSH within the con-
text of the endocrine system’s structure and func-
tion please see the overview section “The
Endocrine System.”
See also ADRENOCORTICOTROPIN HORMONE(ACTH);
ANTIDIURETIC HORMONE (ADH); FOLLICLE-STIMULATING
HORMONE(FSH); GROWTH HORMONE(GH); LUTEINIZING
HORMONE (LH); OXYTOCIN; PARATHYROID GLANDS;
PARATHYROID HORMONE.
thyroid storm A rare but life-threatening condi-
tion resulting from HYPERTHYROIDISMin which the
body experiences an exaggerated response to the
overproduction of thyroid hormones.
Thyroid storm is a medical emergency
that requires rapid treatment.Thyroid storm generates severe ARRHYTHMIAand
tachycardia (disturbances of the HEART’s electrical
activity), high FEVER(disruption of the body’s heat
regulation mechanisms), congestive HEART FAILURE,
significant electrolyte imbalances, and seizures or
psychotic behaviors. Typically thyroid storm devel-
ops when a person who has undiagnosed hyper-
thyroidism, most commonly the result of GRAVES’S
DISEASE, experiences physiologic stress such as
INFECTION, trauma, or surgery. The circulating thy-
roid hormones overwhelm the cells, dramatically
accelerating METABOLISM. The body’s usual nega-
tive-feedback loop mechanisms fail, and the THY-
ROID GLANDcontinues to pour thyroid hormones
into the BLOODcirculation.
Symptoms and Diagnostic PathThe symptoms and signs of thyroid storm manifest
rapidly and include
- severe NAUSEA, VOMITING, and DIARRHEA
- high fever (above 105ºF)
- confusion and anxiety
- DYSPNEA (difficulty BREATHING) and TACHYPNEA
(rapid breathing)
- DYSPNEA (difficulty BREATHING) and TACHYPNEA
- racing or pounding PULSE(140 beats per minute
or greater)
The diagnostic path begins with blood tests to
measure the levels of thyroid hormones. Typically,
THYROXINE(T 4 ) andTRIIODOTHYRONINE(T 3 ) are signifi-
cantly elevated and THYROID-STIMULATING HORMONE
(TSH) is low. However, the diagnosis is primarily
clinical (based on signs and symptoms).Treatment Options and Outlook
Treatment aims to bring thyroid hormone levels
down as quickly as possible, usually with the med-
ications methimazole or propylthiouracil (PTU).
Follow-up administration of intravenous iodine
blocks the thyroid gland from resuming thyroid
hormone production. Plasmapheresis to filter thy-
roid hormones from the blood may be a treatment
option for people who do not respond to these
measures. Beta blocker medications such as
propanolol help thwart the actions of thyroid hor-
mones that reach cells throughout the body. Other
therapies target symptoms, such as cooling to
bring the body temperature down and medica-
tions to regulate the heart’s rhythm. Once the per-
son’s status stabilizes, the endocrinologist typically
begins treatment for the underlying hyperthy-
roidism, which may include surgery to remove the
thyroid gland or radioactive iodine to destroy the
thyroid gland’s ability to produce thyroid hor-
mones.
Without treatment, or when treatment begins
too late, thyroid storm is fatal. With appropriate
and timely treatment about 80 percent of people
who experience thyroid storm survive. After treat-
ment, lifelong HORMONE THERAPYwith thyroid hor-
mone supplement is necessary.Risk Factors and Preventive Measures
The primary risk factor for thyroid storm is undi-
agnosed hyperthyroidism. Appropriate treatment
for hyperthyroidism can eliminate the risk for thy-
roid storm.
See alsoHYPOTHYROIDISM; THYROIDITIS.thyrotoxicosis See HYPERTHYROIDISM.thyrotoxicosis 165