The majority of patients receiving radioactive iodine therapy show improvement in 4-8 weeks, and up to 80% of patients develop hypothyroidism between 2-6 months following treatment. However, post-treatment hypothyroidism can sometimes be transient and self-limited.
TSH may remain suppressed for months after the resolution of hyperthyroidism and does not always indicate ongoing hyperthyroidism. The most appropriate next steps are to obtain T3 and T4 levels, evaluate patient symptoms, and monitor the patient with occasional clinical examinations. This patient has symptoms of hypothyroidism with a suppressed TSH level. If the T3 and T4 levels indicate chemical hypothyroidism, she should be started on levothyroxine (Choice C). If the levels are normal, she should be reassessed again in 4-8 weeks (Choice B).