Thyroid nodules are common, increasingly so with increasing age. The reported incidence varies with the method of assessment. In middle-aged and elderly 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

Most nodules are benign. Benign causes include hyperplastic colloid goiter, thyroid cysts, thyroiditis, and thyroid adenomas. Malignant causes include thyroid cancers (see Thyroid Disorders: Thyroid Cancers).

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's thyroiditis. Risk factors for thyroid cancer include

• History of thyroid irradiation, especially in infancy or childhood
• Age < 20 yr
• Male sex
• Family history of thyroid cancer or multiple endocrine neoplasia type 2
• A solitary nodule
• Dysphagia
• Dysphonia
• Increasing size (particularly rapid growth or growth while receiving thyroid suppression treatment)

Physical examination

Signs that suggest thyroid cancer include stony hard consistency or fixation to surrounding structures, cervical lymphadenopathy, and hoarseness due to recurrent laryngeal nerve paralysis.

Testing

Initial evaluation of a thyroid nodule consists of measurement of levels of

• Thyroid-stimulating hormone (TSH)
• Free thyroxine (T₄)
• Antithyroid peroxidase antibodies

If 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's thyroiditis, fine-needle aspiration biopsy 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 nodules that are entirely cystic. Ultrasonography is rarely diagnostic of cancer, although cancer is suggested by certain ultrasonographic or x-ray findings:

• Fine, stippled, psammomatous calcification (papillary carcinoma)
• Hypoechogenicity, irregular borders, increased intranodular vascularity, height greater than width on transverse section, irregular macrocalcifications, or rarely dense, homogeneous calcification (medullary carcinoma)

Treatment

Treatment is directed at the underlying disorder. Thyroxine suppression of TSH to shrink smaller benign nodules is effective in no more than half the cases.

Last full review/revision May 2012 by Jerome M. Hershman, MD