Thyroid storm

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For patient information, click Thyroid storm

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Synonyms and keywords: Thyrotoxic storm, accelerated hyperthyroidism, hyperthyroid storm

Overview

An unusual but life threatening condition develops in patients with hyperthyroidism either due to poorly controlled pre existing hyperthyroidism or due to medical conditions that precipitate a crisis situation called thyroid storm. There develops a hypermetabolic state that leads to its development. It is mainly a clinical diagnosis and warrants prompt treatment.

Pathophysiology

Thyroid storm is a state of decompensation of the hyperthyroid gland. It could be either due to increased levels of thyroid hormones, increased responsiveness to catecholamines, enhanced response to thyroid hormones at the cellular level, presence of unique catecholamine like substance in hyperthyroidism or due to direct sympathomimetic effect of thyroid hormone due to its structural similarity to catecholamines . The exact cause is not clear. Also, it has been found that it is only the free T4 and T3 that are high. The levels of total T4 and T3 are fairly similar to those found in hyperthyroidism. For a hyperthyroid patient just being intolerant to heat and exhibiting diaphoresis, thyroid storm makes one hyperpyrexic. The enhanced metabolism is translated into increased oxygen and energy consumption. Similarly, moderate tachycardia of hyperthyroidism enhances to hypertension , arrhythmias and possibly high output heart failure. Irritable and restless patient of hyperthyroidism now has agitation, delirium, seizures and could progress to coma. The exact cause behind this heightened effect is unclear.

Causes

Common Causes

• Any surgery

• Direct trauma to the gland

• Recent infection

• Withdrawal or non compliance with antithyroid medication

• Medical stressors like myocardial infarction

• Acute iodine load

• Parturition

Causes by Organ System

Cardiovascular	Medical stressors like myocardial infarction.
Chemical / poisoning	No underlying causes
Dermatologic	No underlying causes
Drug Side Effect	Pseudoephedrine, Salicylates, NSAID, Chemotherapy, excessive thyroid hormone ingestion, Withdrawal or non compliance with antithyroid medication, acute iodine load.
Ear Nose Throat	No underlying causes
Endocrine	TSH secreting tumour, Hyperfunctioning thyroid nodule, Hyperfunctioning multinodular goiter, diabetic ketoacidosis.
Environmental	No underlying causes
Gastroenterologic	No underlying causes
Genetic	McCune Albright syndrome
Hematologic	No underlying causes
Iatrogenic	No underlying causes
Infectious Disease	Recent infection.
Musculoskeletal / Ortho	No underlying causes
Neurologic	No underlying causes
Nutritional / Metabolic	No underlying causes
Obstetric/Gynecologic	Transplacental passage of maternal thyroid hormone immunoglobulins in neonates, toxemia of pregnancy, molar pregnancy, parturition.
Oncologic	No underlying causes
Opthalmologic	No underlying causes
Overdose / Toxicity	No underlying causes
Psychiatric	No underlying causes
Pulmonary	No underlying causes
Renal / Electrolyte	No underlying causes
Rheum / Immune / Allergy	No underlying causes
Sexual	No underlying causes
Trauma	Direct trauma to the gland.
Urologic	No underlying causes
Dental	No underlying causes
Miscellaneous	Anaesthesia induction, vigorous palpation of thyroid gland, any surgery.

Causes in Alphabetical Order

• A...
• Z...

Make sure that each diagnosis is linked to a page.

Epidemiology and Demographics

The frequency of thyroid storm is unknown in children. In a national survey in Japan, incidence of thyroid storm in hospitalized patient was found to be 0.20 per 100,000 per year. If the diagnosis is promptly made and early management initiated, the adult mortality rate is less than 20% contrary to a rate of 90% if patient left untreated.

Age

Children aged 10-15 years account for greater than 2/3rd cases of thyrotoxicosis. Hence, thyroid storm is more common in adolescents though it can occur in any age group.

Gender

Hyperthyroidism is 3-5 times more common in females than males. Incidence of thyroid storm is presumed to be higher in females but no clear data is available.

Natural History, Complications and Prognosis

Congestive heart failure and pulmonary edema can develop rapidly and lead to death.

Diagnosis

History

The patient may be a known case of hyperthyroidism or may present initially with severe symptoms of thyroid storm.

Symptoms

Hyperpyrexia ie. temperature > 104'F, tachycardia > 140/min or Atrial fibrillation and delirium or agitation are typical features of thyroid storm. Other features include -

• General- profuse sweating, poor feeding, weight loss, respiratory distress, fatigue.
• Cardiovascular- pulmonary edema, hypotension, arrhythmia and death from cardiovascular collapse.
• Gastrointestinal- severe nausea, vomiting, diarrhea, abdominal pain, hepatic failure, unexplained jaundice.
• CNS- agitation, anxiety, delirium, psychosis, stupor, seizures and coma.

Burch and Wartofsky introduced a scoring system for identification of thyroid storm. They used criteria like thermoregulatory dysfunction, cardiovascular dysfunction, central nervous system effects, heart failure, gastro-intestinal-hepatic dysfunction and precipitant history. A score >45 is highly suggestive of thyroid storm while score <25 makes it unlikely. A score of 25-44 is suggestive of an impending storm.

Social History

Alcohol

The frequency and amount of alcohol consumption should be characterized.

Physical Examination

Appearance of the Patient

The patient has features of hyperthyroidism like profuse sweating and orbital signs like lid lag etc. The patient would be in a state of agitation or confusion or maybe seizing or could present with coma.

Vital Signs

Thyroid storm is characterized by high fever (>38.5'C or 101.3'F). This may progress to hyperpyrexia (>40'C or 104'F). There could be hypotension or hypertension with a wide pulse pressure. The tachycardia in thyroid storm is out of proportion to the fever. The patient may have heart rate upto 140/min and may progress to atrial fibrillation.

Skin

There will be typical features of hyperthyroidism like warm and moist skin.

Eyes

The eye signs are similar to those found in hyperthyroidism like exophthalmos, lid retraction, lid lag, wide palpebral fissure, staring expression, inability to keep eyeballs converged.

Throat

A palpable goiter may be felt in the neck.

Heart

There would be signs of right sided heart failure like edema, hepatomegaly, ascites, rales, etc. Thyroid storm is associated with supraventricular tachycardia , though ventricular tachycardia can also occur.

Neurologic

The patient would be in altered mental status ranging from agitation, confusion, seizures, stupor and coma. There could be tremors and some pyramidal signs.

Laboratory Findings

The diagnosis of thyroid storm is mainly clinical and if suspected, immediate treatment should begin without waiting for laboratory results. The laboratory findings are similar to hyperthyroidism and are as follows-

• Thyroid function test- elevated free T3 and T4 and may or may not have decreased TSH. There is increased T3 resin uptake and elevated 24 hr iodine uptake.

• Complete blood count- mild leukocytosis with shift to left.

• Liver function test- non specific abnormalities like increase in alanine transaminase(ALT), aspartate transaminase(AST), lactate dehydrogenase(LDH), alkaline phosphatase(ALP) , Creatine Kinase and serum bilirubin.

Electrocardiogram

One could find narrow complex QRS suggestive of supraventricular tachycardia or 3 or more ventricular beats at a rate of 110-250/minute suggestive of ventricular tachycardia. Of the supraventricular tachycardia, atrial fibrillation is the most common one characterized by absent P waves, unorganized electrical activity in their place and irregular R-R interval.

Chest X Ray

Features of cardiomegaly may be found which are suggestive of congestive heart failure. There could also be features of pulmonary edema like increased fluid in alveolar walls, Kerley B lines , increased vascularity in the peri hilum region (classical bat wing appearance) suggestive of pulmonary edema.

CT

In view of features like agitation, confusion, delirium etc, a CT scan of head may be needed to rule out intracranial causes.

Treatment

Pharmacotherapy

The main aims of medical therapy are as follows-

1. Reduce effects of thyroid hormone on peripheral tissues.
2. Decrease further synthesis of thyroid hormone
3. Decrease release of hormone
4. Prevent further TH secretion and peripheral conversion of T4 to T3.

The medications used to accomplish the above aims are described as follows (in order of the aims)-

1) Beta-blockers

Beta blockers block peripheral conversion of T4 to T3. Exercise caution while using in patients with congestive heart failure and cardiomyopathy. They are known to precipitate cardiac arrest in patients with cardiomyopathy.

1. Propanolol- nonselective beta adrenergic antagonist, used widely.
2. Esmolol- beta 1 specific antagonist with a short duration of action.

2) Antithyroids

Propylthiouracil is the drug of choice for thyroid storm that prevents organification, trapping of iodide to iodine and also peripheral conversion of T4 to T3. It is available only as per oral medication and hence comatosed patients may need to be given via nasogastric tube. It causes more rapid decrease in T3 levels than methimazole.

Methimazole has similar mechanism of action as propylthiouracil except it does not inhibit peripheral conversion. It is more potent than propylthiouracil. It is also only available as per oral formulation. It has longer duration of action, used in non life threatening situations. It is less hepatotoxic therefore all patients started on propylthiouracil should be started on methimazole before discharge.

Few patients may be one unable to take antithyroids due to side effects like agranulocytosis, hepatotoxicity and/or allergy. Thyroid storm has been found to develop in patients upon discontinuation of antithyroids. In that case, on should go for a week course of steroid, Lugols iodine, beta blockers and proceed with thyroidectomy on the 8th day.

References

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