A 3-year-old boy is noted to have a 2 cm mass over the thyroid region which has not changed for the past 6-7 months. The child has been healthy but is obese with weight at the 95th percentile and height at the 10th percentile. The thyroid gland is not palpable, and the rest of the exam is normal. What is the next step in evaluation?

1.Thyroid stimulating hormone level
2.Observe in next 6 to 12 months
3.Head and neck MRI
4.Ultrasound