When evaluating a solitary thyroid nodule, the initial test is measurement of which hormone?

When evaluating a solitary thyroid nodule, the initial test is measurement of which hormone?

• A. Calcitonin
• B. T3
• C. TSH
• D. FT4

Answer: (C)

Assessing a solitary thyroid nodule starts with checking how the thyroid is functioning, using serum TSH. This single test quickly shows whether the thyroid is hyperfunctioning, hypofunctioning, or functioning normally, and it guides the next steps. If TSH is suppressed, the nodule is likely autonomously producing hormone. A radionuclide uptake scan is then used to see if the nodule is “hot” (toxic) or if other areas are suspicious; hot nodules are usually benign and change management away from cancer concern, focusing on controlling hormone excess or removing the nodule if needed. If TSH is normal or elevated, the nodule is unlikely to be the source of thyrotoxicosis, so the workup proceeds with a neck ultrasound to characterize features and size, followed by fine-needle aspiration biopsy if ultrasound reveals suspicious features or if the nodule is large enough. Calcitonin, T3, and free T4 have roles in specific contexts (such as medullary thyroid carcinoma risk or broader thyroid function assessment), but they do not guide the initial triage of a solitary thyroid nodule as effectively as TSH.

Assessing a solitary thyroid nodule starts with checking how the thyroid is functioning, using serum TSH. This single test quickly shows whether the thyroid is hyperfunctioning, hypofunctioning, or functioning normally, and it guides the next steps.

If TSH is suppressed, the nodule is likely autonomously producing hormone. A radionuclide uptake scan is then used to see if the nodule is “hot” (toxic) or if other areas are suspicious; hot nodules are usually benign and change management away from cancer concern, focusing on controlling hormone excess or removing the nodule if needed.

If TSH is normal or elevated, the nodule is unlikely to be the source of thyrotoxicosis, so the workup proceeds with a neck ultrasound to characterize features and size, followed by fine-needle aspiration biopsy if ultrasound reveals suspicious features or if the nodule is large enough.

Calcitonin, T3, and free T4 have roles in specific contexts (such as medullary thyroid carcinoma risk or broader thyroid function assessment), but they do not guide the initial triage of a solitary thyroid nodule as effectively as TSH.