A 68-year-old woman is hospitalized for right lower lobe pneumonia and treated with ceftriaxone and azithromycin. On the third hospital day, she develops acute shortness of breath and palpitation. ECG reveals atrial fibrillation with a heart rate of 150/min. Temperature is 39 C (102.2 F) and blood pressure is 100/60 mm Hg. The patient's heart rate improves following intravenous administration of diltiazem. Subsequent laboratory results are as follows: Which of the following is the most likely cause of this patient's abnormal thyroid function tests?

Question

A 68-year-old woman is hospitalized for right lower lobe pneumonia and treated with ceftriaxone and azithromycin.  On the third hospital day, she develops acute shortness of breath and palpitation.  ECG reveals atrial fibrillation with a heart rate of 150/min.  Temperature is 39 C (102.2 F) and blood pressure is 100/60 mm Hg.  The patient's heart rate improves following intravenous administration of diltiazem.  Subsequent laboratory results are as follows:  Which of the following is the most likely cause of this patient's abnormal thyroid function tests?

Quizplus · Accepted Answer

Explanation: 11ec25c8_d3ac_b277_bc81_4b15e721bdfc_MD0003_00 Thyroid function tests often are abnormal in patients with severe, acute illness. Euthyroid sick syndrome (ESS) is a common pattern of thyroid function markers often seen in hospitalized patients. A characteristic feature of ESS is decreased peripheral conversion of T4 to T3 by 5'-monodeiodinase. Factors that suppress conversion of T4 to T3 include: Caloric deprivation Increased glucocorticoid and inflammatory cytokine (eg, tumor necrosis factor, interferon alpha) levels Elevated free fatty acid levels Just as inflammation leads to low T3 levels, it also suppresses TSH (but not to the levels seen with hyperthyroidism). Although a low T3 level initially may be the only indication of ESS (as in this patient), T4 and TSH levels may also decrease as the underlying illness continues. Many experts believe that ESS represents a mild, transient central hypothyroid state that functions to minimize maladaptive catabolism in severe illness. decrease In general, thyroid testing should be avoided in hospitalized patients unless a clear indication is present, as in this patient with acute atrial fibrillation (possibly precipitated by pneumonia). Treatment of ESS with exogenous thyroid hormone (ie, levothyroxine) does not improve clinical outcomes and is not indicated. During recovery, patients may experience a modest, transient increase in TSH levels, which may be misinterpreted as subclinical hypothyroidism. Therefore, follow-up testing should be delayed until the patient has returned to baseline health. (Choice B) Amiodarone and high-dose beta blockers (primarily propranolol), which are sometimes given for atrial fibrillation, can suppress deiodination of T4. However, diltiazem does not have a prominent effect on thyroid metabolism. (Choice C) Hypotensive pituitary infarction is unlikely in this patient because it typically is seen in the setting of significant (ie, requiring multiple transfusions) postpartum hemorrhage due to the increased vascularity of the pituitary during pregnancy. Pituitary (or hypothalamic) injury can cause central hypothyroidism (ie, low T4, low TSH) that in some cases may be difficult to differentiate from ESS due to overlapping laboratory features. In such cases, serum cortisol should be obtained; a normal level (as in this patient) makes overt central hypopituitarism unlikely. (Choice D) Thyroid gland inflammation (ie, thyroiditis) can cause destruction of thyroid follicles and release of preformed thyroid hormone. TSH would be suppressed, but serum levels of T4 would be elevated. Educational objective: Euthyroid sick syndrome (ESS) is a common pattern of thyroid function markers seen in acutely ill and hospitalized patients. Initial findings include a low T3 level; however, as the underlying illness continues, T4 and TSH levels may also decrease. ESS may represent a mild, transient central hypothyroid state that functions to minimize catabolism in severe illness.

A 68-Year-Old Woman Is Hospitalized for Right Lower Lobe Pneumonia