Thyroid emergencies in critically ill cancer patients

Thyroid emergencies are uncommon. However, given the systemic effects of thyroid hormone, dysfunction from severe hypothyroidism or severe thyrotoxicosis requires prompt diagnosis and management on intensive care unit. Both myxedema coma and thyroid storm are clinical diagnoses in which lack of timely therapy can result in fatal consequences. History and physical exam are cornerstones to establishing diagnosis with low threshold to suspect infection as a potential trigger event especially in the immunosuppressed cancer patient. In addition to close observation of cardiorespiratory status, antithyroid drugs for thyroid storm and levothyroxine treatment for myxedema coma, both emergent scenarios require empirical coverage with glucocorticoids until adrenal insufficiency is ruled out. Careful review of medications is important as newer chemotherapeutic agents like tyrosine kinase inhibitors and immune checkpoint inhibitors are known to cause thyroid dysfunction. There are many challenges in interpreting thyroid function tests in the setting of acute illness as patients can present with transient test abnormalities denominated as euthyroid sick syndrome or non-thyroidal illness syndrome (NTIS), which is a physiologic adaptation of the hypothalamic-pituitary-thyroid axis.