Soru

Complaints of a racing heart, persistent heat intolerance, and frequent loose stools have brought a 31-year-old medical assistant to the clinic. She reports unintentionally losing $4$ kg ($8.8$ lb) over the past month. She denies any neck pain, dysphagia, or recent viral illnesses. Her past medical history is unremarkable, and she denies taking any prescribed medications or over-the-counter supplements. Vital signs show a blood pressure of $138/78$ mm Hg and a regular pulse of $112$/min. Physical examination reveals an anxious-appearing woman with a fine, symmetric resting tremor in her outstretched fingers. The neck is supple, and the thyroid gland is not palpable. No proptosis or localized pretibial edema is noted.

Laboratory studies yield the following results:
- Thyroid-stimulating hormone (TSH): $0.02$ $\mu$ U/mL (Normal: $0.4-4.2$ $\mu$ U/mL)
- Free T4: $3.4$ ng/dL (Normal: $0.8-1.8$ ng/dL)
- Free T3: $6.2$ pg/mL (Normal: $2.3-4.2$ pg/mL)

A 24-hour radioactive iodine uptake scan demonstrates an uptake of $1\%$ (Normal: $15\%-30\%$).

Which of the following laboratory findings is most likely present in this patient?