Which parameter in the pituitary hormone cascade is MOST directly responsible for the thyroid storm precipitation in a thyroid storm (Burch-Wartofsky score >45)?
- A Elevated TSH driving unregulated thyroid hormone release
- B TRAb-mediated complement activation and vascular leak
- C Markedly elevated free T3 with beta-adrenergic receptor sensitization ✓
- D Sudden decline in TBG unmasking bound hormone fractions
Correct answer: C. Markedly elevated free T3 with beta-adrenergic receptor sensitization
Explanation
Thyroid storm is characterised by dramatically elevated free T3 (more than free T4), which sensitises adrenergic receptors — this explains the intense adrenergic hyperactivity (tachycardia, hyperpyrexia, agitation). TSH is suppressed, not elevated, in hyperthyroidism. TRAb causes Graves disease but does not directly precipitate the acute storm mechanism. TBG changes alter measured total hormones but free hormone levels are independently regulated.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.