Thyroid Disorders USMLE Step 1 Practice Question
A 70-year-old man is admitted to the ICU with severe sepsis secondary to pneumonia. Vital signs show BP 92/58, HR 118, RR 28, temp 39.2°C, SpO2 88%. Thyroid function tests reveal low T3 (60 ng/dL), normal-low T4 (5.2 mcg/dL), and normal-low TSH (1.8 mIU/L). Chest X-ray confirms bilateral infiltrates. He denies prior thyroid disease and takes no thyroid medications. Which mechanism best explains these thyroid findings?
Answer choices
- AUnregulated secretion of TSH by pituitary adenoma
- BTSH receptor stimulating antibodies
- CAutoimmune destruction of thyroid follicles
- DIncreased peripheral conversion of T4 to T3
- EReduced peripheral conversion of T4 to T3 during severe illnessCorrect answer
- FIncreased hepatic clearance of thyroid hormones due to sepsis-induced hepatocellular injury
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