(See also Overview of Thyroid Function.)
The reported incidence varies with the method of assessment. In middle-aged and older patients, palpation reveals nodules in about 5%. Results of ultrasonography and autopsy studies suggest that nodules are present in about 50% of older adults. Many nodules are found incidentally on thyroid imaging studies done for other disorders.
Etiology
Evaluation
History
Pain suggests thyroiditis or hemorrhage into a cyst. An asymptomatic nodule may be malignant but is usually benign. Symptoms of hyperthyroidism suggest a hyperfunctioning adenoma or thyroiditis, whereas symptoms of hypothyroidism suggest Hashimoto thyroiditis. Risk factors for thyroid cancer include
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History of thyroid irradiation, especially in infancy or childhood
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Age < 20 years
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Male sex
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Family history of thyroid cancer or multiple endocrine neoplasia type 2
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A solitary nodule
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Dysphonia
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Increasing size (particularly rapid growth or growth while receiving thyroid suppression treatment)
Physical examination
Testing
Initial evaluation of a thyroid nodule consists of testing for
If thyroid-stimulating hormone (TSH) is suppressed, radioiodine scanning is done. Nodules with increased radionuclide uptake (hot) are seldom malignant. If thyroid function tests do not indicate hyperthyroidism or Hashimoto thyroiditis, fine-needle aspiration biopsy done under ultrasound guidance is done to distinguish benign from malignant nodules. Early use of fine-needle aspiration biopsy is a more economic approach than routine use of radioiodine scans.
Ultrasonography is useful in determining the size of the nodule; fine-needle aspiration biopsy is not routinely indicated for nodules <1 cm on ultrasonography or for nodules that are entirely cystic. Ultrasonography is rarely diagnostic of cancer, although cancer is suggested by certain ultrasonographic or x-ray findings:
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Fine, stippled, psammomatous calcification (papillary thyroid carcinoma)
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Hypoechogenicity, irregular borders, height greater than width on transverse section, irregular macrocalcifications, or rarely dense, homogeneous calcification (medullary thyroid carcinoma)
