Question

A $28$-year-old woman comes to the clinic complaining of palpitations, excessive sweating, and a $5\text{ kg}$ ($11\text{ lb}$) weight loss over the past $6$ weeks despite an increased appetite. She has a history of major depressive disorder, for which she takes fluoxetine. She is a competitive bodybuilder and reports feeling immense pressure for an upcoming competition. Vital signs show a temperature of $37.2^\circ\text{C}$ ($99.0^\circ\text{F}$), blood pressure of $145/75\ \text{mmHg}$, and a pulse of $112\text{/min}$. Physical examination reveals a fine resting tremor, brisk deep tendon reflexes, and warm, moist skin. The thyroid gland is nonpalpable, and there is no exophthalmos.

Laboratory results are as follows:

* Thyroid-stimulating hormone (TSH): $<0.01 \ \mu\text{U/mL}$ (Normal: $0.4-4.0 \ \mu\text{U/mL}$)
* Free T4: $0.3 \ \text{ng/dL}$ (Normal: $0.9-2.4 \ \text{ng/dL}$)
* Free T3: $8.5 \ \text{pg/mL}$ (Normal: $2.0-4.4 \ \text{pg/mL}$)
* Radioactive iodine uptake ($24$-hour): $1\%$ (Normal: $10\%-30\%$)

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