A 74-year-old man is brought to the emergency department after being found outside early on New Year's morning. His medical history is unknown. Temperature is 31.5 C (88.7 F), blood pressure is 75/50 mm Hg, pulse is 55/min, and respirations are 8/min and shallow. On examination, the patient is unresponsive. Initial laboratory results are as follows: Blood alcohol level is undetectable and urine drug screen is negative. Plasma cortisol and ACTH levels are normal. Chest x-ray reveals a right lower lobe infiltrate. The patient is placed on mechanical ventilation, pressor support, warm intravenous fluids, and broad-spectrum antibiotics. Blood cultures are pending. His vital signs improve rapidly with rewarming. Which of the following is the best next step in management of this patient's thyroid abnormalities?

Question

A 74-year-old man is brought to the emergency department after being found outside early on New Year's morning.  His medical history is unknown.  Temperature is 31.5 C (88.7 F), blood pressure is 75/50 mm Hg, pulse is 55/min, and respirations are 8/min and shallow.  On examination, the patient is unresponsive.  Initial laboratory results are as follows:  Blood alcohol level is undetectable and urine drug screen is negative.  Plasma cortisol and ACTH levels are normal.  Chest x-ray reveals a right lower lobe infiltrate.  The patient is placed on mechanical ventilation, pressor support, warm intravenous fluids, and broad-spectrum antibiotics.  Blood cultures are pending.  His vital signs improve rapidly with rewarming.  Which of the following is the best next step in management of this patient's thyroid abnormalities?

Quizplus · Accepted Answer

Explanation: 11ec2b69_beb9_a31f_8f63_fd39b296b5b7_MD0005_00 Euthyroid sick syndrome (ESS) encompasses a variety of alterations in thyroid physiology, the most common of which is termed "low T3 syndrome" and is thought to be primarily the result of decreased conversion of T4 to T3. T4 is produced exclusively in the thyroid gland, whereas T3 is produced mainly by peripheral conversion of T4 by deiodination. Factors in acute illness that inhibit peripheral deiodination include high endogenous cortisol levels, inflammatory cytokines (eg, tumor necrosis factor), starvation, and certain medications (eg, glucocorticoids, amiodarone). TSH and T4 levels are often normal in ESS, although they also may fall in severe or prolonged cases, and ESS may represent a transient central hypothyroidism rather than a true euthyroid state. This patient with pneumonia (given leukocytosis and lobar infiltrate on chest x-ray) and shock had thyroid function testing to evaluate hypothermia and bradycardia, but these vital sign abnormalities were likely compounded by cold exposure as they improved significantly with rewarming. The patient's results showing low T3, normal free T4, and normal TSH are consistent with ESS due to acute pneumonia and cold exposure. ESS is considered by some experts to be an adaptive response to stress, and thyroid hormone supplementation in ESS has not been found to improve clinical outcomes. Treatment should therefore be deferred unless abnormal thyroid function persists after the patient has returned to baseline health (Choice D). (Choice A) Antithyroid peroxidase antibodies are a marker for chronic lymphocytic (Hashimoto) thyroiditis. They are also a predictor of progression to overt hypothyroidism in patients with subclinical hypothyroidism (normal T4, elevated TSH). They are not useful in the acute evaluation of patients with normal TSH. (Choice B) Reverse T3 (rT3) is an inactive metabolite of T4. In severe nonthyroidal illness (eg, ESS), clearance of rT3 is reduced and levels will be elevated. rT3 is primarily used in patients with low TSH to differentiate central hypothyroidism (low T4 leads to low rT3) from ESS. (Choice E) T3 has a very short half-life, and treatment with liothyronine (oral T3 supplement) produces wide fluctuations in blood levels. Therefore, liothyronine supplementation is not recommended for routine use. Educational objective: Euthyroid sick syndrome is often characterized by low T3 levels with normal TSH and T4 in patients with acute illness. It is primarily due to decreased peripheral conversion of T4 to T3. Treatment is not recommended unless abnormal thyroid function persists after the patient has returned to baseline health. References: Nonthyroidal illness syndrome. (http://www.ncbi.nlm.nih.gov/pubmed/23974778)

A 74-Year-Old Man Is Brought to the Emergency Department After