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  • Virtually all patients admitted to an ICU have low levels of serum triiodothyronine (T3), and 30% to 50% have low levels of thyroxine (T4) with normal or low levels of serum thyrotropin (TSH).

  • Patients who have a T4 level of less than 3.0 µg/dL, despite normal levels of T4-binding proteins, have a 68% to 84% mortality rate.

  • T3 is the logical choice for critically ill patients requiring thyroid hormone replacement.

  • Early intubation and mechanical ventilation are crucial for the successful treatment of myxedema coma.

  • Glucocorticoid administration, while assessing adrenal status and before thyroid hormone replacement, is critical in the management of myxedema coma.

  • Alterations in thyroid function change the metabolism of almost all drugs, and the doses need careful adjustment to prevent drug toxicity or decreased efficacy.

  • Autonomous hypersecretion and exogenous overdose of thyroid hormone are the most common causes of severe thyrotoxicosis.

  • Hyperpyrexia and altered mental status are the hallmarks of thyroid storm.

  • Medical treatment of severe hyperthyroidism usually normalizes circulating thyroid hormone levels in 2 to 3 weeks, except under circumstances of iodine overload (ie, amiodarone-induced thyroiditis type II), in which case hyperthyroxinemia may persist for months.

  • Blockade of hormonal secretion is best accomplished by the addition of stable iodine to an antithyroid drug regimen.

  • In severe thyrotoxicosis, treatment with iopanoic acid can be lifesaving (although this is not available in the United States).

  • β-Blockers prevent thyroid storm in thyrotoxic patients undergoing surgery, and they may ameliorate cardiovascular dysfunction in thyroid storm, but their side effects often interfere with therapy in the elderly, in patients with asthma, and in patients with cardiomyopathy.

  • Amiodarone-induced thyrotoxicosis in a critically ill patient should be managed with methimazole (30-50 mg/d), potassium perchlorate (500 mg twice a day) (not available in the United States), and prednisone (30-40 mg/d).

  • In cases of levothyroxine overdose only symptomatic and supportive treatment is needed.

  • Neonatal thyrotoxicosis can be life-threatening; it is usually caused by transplacental transfer of thyroid-stimulating antibodies. It is transient and requires only short-term treatment.


Perhaps the most controversial if not the most challenging aspect of thyroidology in ICU setting is how to interpret thyroid function tests in critically ill patients and what to do when test results are abnormal.


Definition of Nonthyroidal Illness Syndrome

Virtually all critically ill patients have reduced serum levels of triiodothyronine (T3), and approximately 30% to 50% also have low levels of thyroxine (T4), both associated with normal or low serum TSH values (10%).1 This phenomenon has been termed low T3 syndrome, nonthyroidal illness (NTI), or euthyroid sick syndrome. Each of these descriptive terms assumes a priori that such patients are euthyroid despite reduced thyroid hormone levels. The condition is ...

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