The treatment of thyroid storm includes the following:
1. Inhibition of new hormone synthesis with thiouracils (PTU) or imidazoles (methimazole and carbimazole)
PTU blocks the enzyme thyroidal peroxidase to inhibit thyroid hormone synthesis. It is generally preferred over methimazole because it also inhibits the peripheral conversion of T4 to T3. The dose of PTU is a 500-1000 mg loading dose, followed by 250 mg every 4 hours. Methimazole is dosed 60-80 mg/day in divided doses.
2. Blockade of release with iodine or lithium
Blocking release of thyroid hormone is best accomplished with iodine, but lithium can be used in iodine-allergic patients. It is important not to administer iodine until after the synthetic pathways have been blocked with PTU (at least 30 minutes), otherwise administration of iodine might cause more thyroid hormone to be formed.
3. Inhibition of peripheral effects with β-adrenergic agents
Propranolol is the preferred treatment to block peripheral effects of thyroid hormone because of its non-selective effects and the additional benefit of inhibiting peripheral conversion of T4 to T3. If a contraindication to propranolol exists (e.g. asthma, congestive heart failure), then a selective agent such as esmolol may be used.
4. Inhibition of Enterohepatic Circulation of Thyroid Hormone
Thyroid hormone is metabolized in the liver where it is conjugated to glucuronides and sulfates and excreted into the intestine in bile, while unconjugated free hormones are reabsorbed into circulation. Cholestyramine, by binding conjugated products, promotes their excretion, thereby lowering thyroid hormone levels. The recommended dosing regimen is 1-4 g twice daily.
5. Additional treatment considerations
Inciting events should be addressed (e.g. infection, DKA, trauma, etc.). Administration of glucocorticoids is recommended because thyroid storm can precipitate adrenal crisis (relative adrenal insufficiency), with similar dosing regimens. Dexamethasone may be preferred, as it also blocks the peripheral conversion of T4 to T3. Antipyretics and external cooling methods may be considered, but salicylates should be avoided as they may increase free hormone levels. Most patients will benefit from IV fluids to replace significant volume loss from hyperthermia and GI losses. Patients failing medical therapy may require surgical intervention.