Critical Care Medicine

Thyroid Disorders: Thyroid Storm

Thyroid Storm

Also known as: Hyperthyroid crisis, thyroid crisis, thyrotoxic crisis

1. Description of the problem

What every clinician needs to know

Thyroid storm is a rare, life-threatening complication of thyrotoxicosis, which is usually precipitated by an intercurrent medical problem.

Hyperthyroidism is the most common cause of thyrotoxicosis leading to thyroid storm. While the cause of the rapid clinical decompensation is unknown, a sudden inhibition of thyroid hormone binding to plasma proteins by the precipitating factor(s), causing an acute rise in the free hormone pool, may play a role in the pathogenesis of thyroid storm. Thyroid storm is a medical emergency that should be managed in the intensive care unit (ICU).

Table I. Precipitating factors of thyroid storm

Table I.

Precipitating Factors of Thyroid Storm
Infections
Stress
Trauma
Thyroidal and nonthyroidal surgery
Diabetic ketoacidosis
Heart and vascular disease
Iodinated contrast studies
Thyroid hormone overdose
Radioactive iodine treatment (especially if there was no pre-treatment with antithyroid drugs)
Labor

Clinical features

Thyroid storm is primarily a clinical diagnosis, with features similar to those of thyrotoxicosis but more exaggerated (Table II). Coma and death may occur in up to 20% of patients, frequently due to cardiac arrhythmias, congestive heart failure, hyperthermia or the precipitating illness. There are no distinct laboratory abnormalities. Thyroid hormone levels are similar to those found in uncomplicated thyrotoxicosis; there is little correlation between the degree of elevation of thyroid hormone and the presentation of thyroid storm.

Table II.

Clinical Features of Thyroid Storm
*Fever (as high as 105.8 degrees F)
*Tachycardia/tachyarrhythmias/atrial fibrillation
*Delirium/agitation/mental status changes
Congestive heart failure
Tremor
Nausea and vomiting
Sweating
Vasodilatation
Dehydration
Hepatomegaly
Splenomegaly
Jaundice

Key management points

Thyroid storm is a major medical emergency that must be treated in an intensive care unit. Treatment should target the following four areas: 1) supportive measures, 2) control of tachyarrhythmias, 3) inhibition of thyroid function and 4) treatment of the underlying precipitating illness.

2. Emergency management

Thyroid storm is a major medical emergency that must be treated in an intensive care unit. A summary of treatment procedures appears in Table III.

Table III.

Treatment of Thyroid Storm
Supportive TherapyTreatment of underlying illnessesIntravenous fluidsCooling blanket and/or antipyretics
Beta-adrenergic blocking drugsPropranolol1mg IV/min to a dose of 10mg then 40–80 mg PO q6hOREsmolol 500mg/kg/min IV then 50–100mg/kg/minORMetoprolol 100–400mg PO q12hORAtenolol 50–100mg PO daily
Antithyroid DrugsInhibition of thyroid hormone synthesisPropylthiouracil 800mg PO first dose then 200–300 mg PO q8h, ORMethimazole 80mg PO first dose then 40–80 mg PO q12hBlock release of thyroid hormones from the glandSSKI - 5 drops PO q8hORLugol’s solution – 10 drops PO q8hORLithium 800–1200mg PO qd – achieve serum lithium levels 0.5 – 1.5 meq/L
Block T4 to T3 conversionCorticosteroids – Dexamethasone 1–2mg PO q6h Most beta-blockers – Propranolol 40–80mg PO q6hPropylthiouracilTelapaque (iopanoic acid) – no longer available in the USA
Remove thyroid hormones from the circulationPlasmapheresis, ORPeritoneal dialysis, ORCholestyramine 4g PO q6h, ORColestipol 20–30mg PO daily
Treatment of the underlying/precipitating illness

Management points not to be missed

Antithyroid drugs need to be started before administration of any iodine-containing compound, whether that compound is SSKI or Lugol's solution or IV contrast media. In fact, if thyroid storm is considered as a diagnosis and the patient needs an imaging procedure that requires IV contrast, it is better to give a one-time dose of methimazole (20–40 mg) or PTU (200–300 mg) prior to the procedure before the diagnosis is confirmed.

Any iodine load in the absence of antithyroid blockade will exacerbate the hyperthyroid state and prolong the time to recovery.

3. Diagnosis

Diagnostic criteria

Thyroid storm is primarily a clinical diagnosis, with features similar to those of thyrotoxicosis, but more exaggerated. The physician must have a high clinical index of suspicion for thyroid storm, as therapy must be instituted before the return of thyroid function tests in most cases. Clues to the diagnosis of thyroid storm are a history of thyroid disease, history of iodine ingestion and the presence of a goiter or stigmata of Graves disease.

Cardinal features include fever, tachycardia/tachyarrhythmias and mental status changes. Thyroid storm should be considered in any patient presenting with this triad, especially if there is accompanying evidence of a goiter, thyroid ophthalmopathy and tremors.

Burch and Wartofsky have published a modified Apache score for the diagnosis of thyroid storm ( Table IV). The diagnosis of thyroid storm was possible with a score of 25 to 45 and is likely with a score greater than 45. Thyroid storm is unlikely with a score lower than 25.

Table IV.

Clinical Scoring System for the Diagnosis of Thyroid Storm
Temperature (degrees Fahrenheit) Score
99–99.9 5
100-100.9 10
101-101.9 15
102-102.9 20
103-103.9 25
>104 30
CNS Effects
Absent 0
Mild agitation 10
Moderate 20
Severe 30
Precipitant History
None 09
Present 10
GI-Hepatic
Absent 0
Moderate 10
Severe (Jaundice) 30
Pulse
90-109 5
110-119 10
120-129 15
130-139 20
>140 25
Congestive heart failure
Absent 0
Mild 5
Moderate 10
Severe 15
AFib
Absent 0
Present 10

Thyroid function tests in thyroid storm

There are no distinct laboratory abnormalities and thyroid hormone levels are similar to those found in uncomplicated thyrotoxicosis; there is little correlation between the degree of elevation of thyroid hormones and the presentation of thyroid storm.

Thyroid function tests should be obtained, including an estimate of the free thyroxine concentration (FT4 or FTI), the total T3 concentration and the thyroid stimulating hormone (TSH) concentration. A total T4 value on its own is of limited or no usefulness. A free T3 by analog is a less accurate test than a total T3 in this clinical situation. Thyroid antibodies may provide an etiology of the underlying thyroid disorder but play no role in the acute management.

Similarly, imaging studies such as nuclear thyroid scanning have no role in the initial management of thyroid storm.

Other laboratory values in thyroid storm

Abnormal liver function tests are common. Hypocalcemia may be observed because of increased osteoclast-mediated bone resorption in the hyperthyroid patient. Hematocrit concentrations may be elevated owing to volume contraction, and leukocytosis is common, even in the absence of infection.

How do I know this is what the patient has?

Any patient with fever, tachyarrhythmias and mental status changes In the setting of increased FT4/FTI and T3 levels and suppressed TSH levels should be considered to have thyroid storm until proven otherwise.

Differential diagnosis

The differential diagnosis of thyroid storm includes sepsis, neuroleptic malignant syndrome, malignant hyperthermia, and acute mania with lethal catatonia, all of which can precipitate thyroid storm in the appropriate setting.

Are there specific confirmatory tests that I should perform?

None outside of thyroid function tests (FT4/FTI, total T3 and TSH)

4. Specific Treatment

See Table III. Treatment of Thyroid Storm

What do I do about particularly refractory cases?

In patients who have not responded to medical therapy with antithyroid drugs, steroids and iodine, removal of the thyroid hormones from the circulation by plasmapheresis or peritoneal dialysis can be performed.

5. Disease monitoring, follow-up and disposition

Follow-up

Management of the patient with thyroid storm in the ICU setting should be continued until the clinical score for thyroid storm drops below 25. Repeat FT4/FTI and total T3 levels should be repeated daily in the patient who is not clinically improving. If the patient is stabilized, repeat FT4/FTI and total T3 levels can be performed on an outpatient basis. After hte initial TSH determination, there is no need to repeat a serum TSH for at least 6 to 8 weeks, as it will remain suppressed for at least that length of time.

Expected response to treatment

There should be stabilization and clearing of the patient's mental status within 24 to 48 hours in the patient who is responding to treatment.

When should I suspect I've made the wrong diagnosis?

While there is little correlation with thyroid function tests and thyroid storm, a slightly low TSH that remains in the detectable range or a suppressed TSH with FT4/FTI and total T3 in normal range makes the diagnosis untenable.

Pathophysiology

While the cause of the rapid clinical decompensation in thyroid storm is unknown, a sudden inhibition of thyroid hormone binding to plasma proteins by the precipitating factor(s), causing an acute rise in the free hormone pool, may play a role in the pathogenesis of thyroid storm. Currently, thyroid storm appears most commonly following infection, causing the thyrotoxic state to decompensate. Pneumonia, upper respiratory tract infections and enteric infections are common precipitating infections.

Other precipitating factors include stress, trauma, nonthyroidal surgery, diabetic ketoacidosis, labor, heart disease, and iodinated contrast studies in the unrecognized or partially treated hyperthyroid patient. Iatrogenic thyroid storm has been reported due to thyroid hormone overdose.

Thyroid storm occurring after 131I therapy is extremely rare, especially considering the frequency of the use of radioiodine in the definitive treatment of hyperthyroidism. When reported, radioiodine-induced thyroid storm usually occurs if there was no pretreatment with antithyroid drugs.

Epidemiology

The historical incidence of thyroid storm was relatively high due to a liberal definition of the condition. For example, some reports included all postoperative thyroidectomy cases manifesting a febrile reaction greater than 38.3 degrees C, Many, if not most, of these early cases do not fit the current criteria for thyroid storm.

Thyroid storm in the postoperative period is rarely observed currently as patients are better prepared for surgery by current standards. Certain clinical and socioeconomic factors have also been suggested to be associated with complicated hyperthyroidism, including the lack of insurance, age less than 30 or greater than 50, and serum T4 concentrations greater than twice the upper limit of normal.

Prognosis

Thyroid storm is a life-threatening illness that carries with it up to a 20% incidence of coma and death, frequently due to cardiac arrhythmias, congestive heart failure, hyperthermia or the precipitating illness.

What's the evidence?

Thyroid Storm

Burch, HB, Wartofsky, L. "Life-threatening thyroitoxicosis: Thyroid storm". Endocrinol Metab Clin North Am. vol. 22. 1993. pp. 263-77.

(Classic article describing a modified Apache score to diagnose thyroid storm.)

Nayak, B, Burman, K. "Thyrotoxicosis and thyroid storm". Endocrinol Metab Clin North Am. vol. 35. 2006. pp. 663-86.

(In-depth reviews on the pathophysiology, presentation and management thyroid storm.)

Yeung, SC, Go, R, Balasubramanyam, A. "Rectal administration of iodide and propylthiouracil in the treatment of thyroid storm". Thyroid. vol. 5. 1995. pp. 403-5.

(This study documents alternatives to oral administration of antithyroid drugs.)

Duggal, J, Singh, S, Kuchinic, P, Butler, P, Arora, R. "Utility of esmolol in thyroid crisis". Can J Clin Pharmacol. vol. 13. 2006. pp. e292-5.

(Adjunctive therapies are important in the management of thyroid storm. This study documents a potentially useful therapeutic option.)

Vijayakumar, V, Nusynowwitz, ML, Ali, S. "Is it safe to treat hyperthyroid patients with I-131 without fear of thyroid storm?". Ann Nucl Med. vol. 20. 2006. pp. 383-5.

(This study addresses the risk of thyroid storm after I131 therapy.)

Lazarus, JH, Addison, AJ, Richards, AR. "Treatment of thyrotoxicosis with lithium carbonate". Lancet. vol. 2. 1974. pp. 1160-3..

Shakir, KM, Michaels, RD, Hays, JH, Potter, BB. "The use of bile aced sequestrants to lower serum thyroid hormone concentrations in iatrogenic hyperthyroidism". Ann Intern Med. vol. 118. 1993. pp. 112-3.

(Adjunctive therapies are important in the management of thyroid storm. This study documents a potentially useful therapeutic option.)(Adjunctive therapies are important in the management of thyroid storm. This study documents a potentially useful therapeutic option.)

Candrina, R, DiStefano, O, Spandrio, S. "Treatment of thyrotoxic storm by charcoal plasmaperfusion". J Endocrinol Invest. vol. 12. 1989. pp. 133-4.

(Adjunctive therapies are important in the management of thyroid storm. This study documents a potentially useful therapeutic option.)
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