Also called thyrotoxic crisis, thyroid storm is a life-threatening hyperthyroid state characterised by multi-system involvement. It is the dangerous end of the spectrum of thyrotoxicosis.
Thyroid storm is rare (maybe 0.5 cases per 100,000 person-years)
Aetiology
The mechanism of thyroid storm is poorly understood but, as usual, several hypotheses have been proposed. The long and short of it is that there is too much of the thyroid hormones; interestingly enough there isn’t significantly more than in boring old hyperthyroidism.
In patients with underlying hyperthyroidism, particularly those with Graves’ disease, many factors may precipitate it.
- Abrupt discontinuation of antithyroid medicine.
- Thyroid (or non-thyroid) surgery.
- Acute iodine load (including amiodarone administration)
- Various acute illnesses.
- Burns.
- Stroke or traumatic brain injury.
- Parturition
Mechanisms
The authors simple mind has no capacity for the complex theories of the pathophysiology of thyroid storm, and theories abound. Simply, the thyroid hormones modulate the basal metabolic rate and more thyroid means faster BMR, this explains pretty much all of the manifestations below. There is also some talk about the increased expression of beta1 adrenergic receptors and beta blockade is as essential tenet of treatment but to mull over this further is probably academic.
Clinical manifestations
Thyroid storm is essentially just profound hyperthyroidism with multi-system (up) dysregulation and an acute precipitating event. In the case of no obvious precipitating event, Henry Burch and Leonard Wartofsky have developed a scoring system for the likelihood of the patients symptoms to represent a thyroid storm.1
That article is only available in print at the authors alma mater, but the scale is succinct enough it needn’t be duplicated here. Thus, detailed below are the broad physiological manifestiations:
- Fever.
- Tachycardia, potentially leading to tachyarrythmia and heart failure.
- CNS involvement such as agitation, anxiety, restlessness, psychosis, or coma.
- Various gastrointestinal symptoms (simple nausea and vomiting to acute liver failure).
- The usual thyrotoxic suspects: tremor, goitre, hyperreflexia, hypertension, and exophthalmos.
Laboratory hyperthyroidism is usually also present but diagnosis and treatment can’t really wait for these results: the mortality rate of thyroid storm is greater than 10% in Japan.2
Management
The principles of management are to reverse the effects of the storm by suppressing the action of thyroid hormones, and also limiting the synthesis and activation of thyroid hormones.
Beta blockade
Most of the danger is in the cardiovascular effects and beta blockade targets this. It may improve the heart failure (and even prop up the blood pressure). Good old fashioned propanalol is still the winner here as it also reduces the conversion of T4 to T3 in the peripheral tissues. Esmolol doesn’t, but is easy to titrate because it is “quick on and quick off”.
Thionamides
Propylthiouracil and methimazole (or carbimazole which is metabolised to methimazole anyway) both inhibit thyroperoxidase which means no more iodination of thyroglobulin and, therefore, no more thyroid hormones. PTU also has a not insignificant effect on T4 to T3 conversion peripherally It is essential to note here that the primordial thyroid hormones are already waiting in the colloid for proteolysis and secretion which needs to be prevented another way.
Lugol’s iodine
Administration of iodine inhibits T4 and T3 release by inhibiting proteolysis and apparent also MCT8. This is called Plummering after the eponymous name of the effect.
Steroids
Steroids are also used to inhibit conversion of T4 to T3 peripherally. Iodinated contrast is probably the better way to do this but people do worry so much about the kidneys.
Further reading
- Yartsev A. Hyperthyroidism and thyrotoxicosis. Deranged Physiology. 2025. Link
Footnotes
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Burch HB, Wartofsky L. Life-threatening thyrotoxicosis. Thyroid storm. Endocrinol Metab Clin North Am. 1993 Jun;22(2):263–77. ↩
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Akamizu T, Satoh T, Isozaki O, Suzuki A, Wakino S, Iburi T, et al. Diagnostic criteria, clinical features, and incidence of thyroid storm based on nationwide surveys. Thyroid. 2012 Jul;22(7):661–79. ↩