In evaluating a thyroid nodule, which test is best used initially?

• A. Thyroid function test
• B. Ultrasound
• C. FNA
• D. RAIU

Answer: (A)

When a thyroid nodule is found, the first step is to assess thyroid function with a thyroid function test (TSH). This determines whether the gland is hyper-, hypo-, or euthyroid, which directly influences next steps in management. If TSH is low, the nodule may be a functioning (toxic) nodule, and the immediate focus shifts toward treating hyperthyroidism rather than biopsy, since cancer risk is lower in hyperfunctioning nodules. If TSH is normal or elevated, imaging with ultrasound becomes the key next step to characterize the nodule’s structure and features and to decide if a fine-needle aspiration is warranted. Radioactive iodine uptake is a useful tool in evaluating hyperthyroidism but is not appropriate as the initial test.