Diagnosing Thyroid Nodules
The initial laboratory assessment of a thyroid nodule includes the measurement of thyroid-stimulating hormone (TSH), T3, and T4. These results will determine if the thyroid gland is functioning properly or if there is an issue like hyperthyroidism or hypothyroidism. Most patients with a solitary thyroid nodule have normal levels of TSH.1
Serum antithyroid peroxidase (anti-TPO) antibody and antithyroglobulin (anti-Tg) antibody levels are important diagnostic tools if the patient has relevant history suggesting the possibility of an autoimmune disorder like Hashimoto thyroiditis.1
Fine-Needle Aspiration Biopsy (FNAB)
FNAB is currently the most important diagnostic tool for thyroid nodules. Using a very fine needle, a doctor can gather a sample of thyroid tissue to diagnose the underlying condition. This procedure is usually quite simple and can be performed in a doctor’s office with local anesthesia.
The results of the FNAB can be divided into:
- Benign: the lesion has less than a 1% chance of being malignant.
- Atypia: the lesion has a 5 to 10% chance of being malignant.
- Follicular neoplasm: the lesion has a 20 to 30% chance of being malignant.
- Suspicious for malignancy: the lesion has a 50 to 75% chance of being malignant.
- Malignant: the lesion has a 100% chance of being malignant.
- Nondiagnostic: not enough cells were gathered, therefore a diagnosis cannot be obtained.
The use of ultrasound-guided FNAB yields better results and decreases the chance of having a nondiagnostic result, even on cystic or predominantly cystic nodules.1
This is a nuclear imaging study that uses radioactive isotopes to assess thyroid function. Nuclear imaging of the thyroid can be used to establish if a nodule is hot (hyperfunctioning), warm (normal), or cold (hypofunctioning).
This procedure is no longer a first-line option due to its high cost and the fact that there are better diagnostic tools available.
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The above information explains what is involved and the possible risks. It is not meant to be a substitute for informed discussion between you and your doctor, but can act as a starting point for such a discussion.