Question

A $31$-year-old woman, gravida $2$, para $1$, presents to the clinic for her initial prenatal visit at $11$ weeks gestation. She reports mild nausea and breast tenderness but otherwise feels well. She has no significant past medical history and takes only a daily prenatal vitamin. Her blood pressure is $112/70\text{ mm Hg}$ and pulse is $84/\text{min}$. Physical examination reveals a normal-sized thyroid gland without palpable nodules or tenderness. Pelvic examination is consistent with an $11$-week gestation. Routine initial prenatal laboratory studies are obtained, and the results of a reflexively drawn thyroid panel are as follows:

Thyroid-stimulating hormone (TSH): $0.15\ \mu\text{U/mL}$ (Reference: $0.4\text{--}4.0\ \mu\text{U/mL}$)
Total thyroxine (T4): $14.8\ \mu\text{g/dL}$ (Reference: $5.0\text{--}12.0\ \mu\text{g/dL}$)
Free thyroxine (T4): $1.6\text{ ng/dL}$ (Reference: $0.8\text{--}1.8\text{ ng/dL}$)

Which of the following is the most appropriate next step in management?