Question

A $45$-year-old woman is evaluated in the clinic for a $4$-month history of constant palpitations, excessive sweating, and a $6\text{-kg}$ ($13.2\text{-lb}$) weight loss despite a significantly increased appetite. She also reports new, persistent bi-frontal headaches and recently sideswiped a vehicle while driving, stating she "did not see the car in the next lane." Physical examination reveals warm, moist skin, a fine resting tremor of the outstretched hands, and a diffusely enlarged, non-tender thyroid gland without palpable nodules. Confrontational visual field testing demonstrates diminished peripheral vision bilaterally. Vital signs show a heart rate of $110/\text{min}$ and blood pressure of $145/85\text{ mm Hg}$. A urine pregnancy test is negative.

Laboratory results are as follows:
- Thyroid-stimulating hormone (TSH): $5.8\text{ mU/L}$ (Normal: $0.5\text{ - }5.0\text{ mU/L}$)
- Free thyroxine (T4): $3.2\text{ ng/dL}$ (Normal: $0.9\text{ - }1.7\text{ ng/dL}$)
- Free triiodothyronine (T3): $6.5\text{ pg/mL}$ (Normal: $2.0\text{ - }4.4\text{ pg/mL}$)

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