Laboratory Studies
Initial screening should include TSH. Given the sensitive third-generation assays, in the absence of symptoms of hyperthyroidism or hypothyroidism, further testing is not required. An assessment of free thyroxine index or direct measurement of free thyroxine would be the next step in the evaluation.
Further laboratory testing is based on presentation and results of screening studies and may include thyroid antibodies (antithyroid peroxidase; formerly, the antimicrosomal antibodies and antithyroglobulin), thyroglobulin, sedimentation rate, and calcitonin in an individual at high risk for medullary carcinoma of the thyroid.
Imaging Studies
Ultrasonography
Ultrasonography can be used to establish and follow goiter size, consistency, and nodularity. [3] It can also be employed to localize nodules for ultrasonographically guided biopsy.
A study by Kelly et al indicated that in some patients with multinodular goiter, the risk of neoplasia can be effectively assessed with ultrasonography rather than with fine-needle aspiration biopsy. The investigators reported that in study patients with no suspicious features on ultrasonography, the average risk of neoplasia in multinodular goiters was 0.0339, although this risk rose significantly when one or more suspicious features were present. [15]
Roentgenography
Roentgenography is used to assess extent of a goiter and presence of calcification. Ultrasonography has replaced this modality.
Roentgenography is used to visualize calcifications within a goiter and regional lymph glands.
Computed tomography (CT) scanning
CT scanning is more precise than roentgenography.
CT scanning can be used to delineate size and goiter extent. Due to the superficial placement of the thyroid gland, ultrasonography is more useful in following size. CT scanning does a much better job of determining the effect of the thyroid gland on nearby structures. It also may be useful in the follow-up of patients with thyroid cancer that shows evidence of recurrence.
CT scanning can be used to guide biopsy of the thyroid.
MRI
Magnetic resonance imaging has the same indications as CT scanning (see above).
Radionuclide uptake and radionuclide scanning are used to assess thyroid function and anatomy in hyperthyroidism, as shown below. Additionally, thyroid scanning may be useful in the patient with neck or superior mediastinal masses. Radionuclide scanning allows determination of the function of a nodule. Function of a thyroid nodule has value both diagnostically and therapeutically. See the image below.
Thyroid nuclear scan of a patient with a euthyroid goiter showing different projections.
Other
Barium swallow is used to assess esophageal obstruction.
Spirometry: The flow-volume loop is useful in determining the functional significance of compressive goiters.
Perchlorate discharge test is used in individuals with inborn errors of thyroid hormone synthesis. It is used rarely today to determine the ability to trap and organify iodine.
Procedures
Fine-needle aspiration biopsy is used for cytologic diagnosis. [4] Fine-needle aspiration of the thyroid is used to determine the cause of an enlarged gland. In general, the procedure is not used in the workup of autonomously functioning nodules. The procedure has little morbidity and can be tailored to the situation.
Core biopsy, or large-needle biopsy, of the thyroid uses a larger-gauge needle, providing a fragment of tissue. This procedure also carries with it a higher morbidity. Core biopsy has the advantage of more complete sampling.
Partial thyroidectomy may be used as a first-line procedure for patients with a high probability of cancer. It is reserved mostly if the result of a fine-needle aspiration is suspicious or if the patient/physician prefers it.
Total thyroidectomy is performed for malignant goiters.
Histologic Findings
Simple nontoxic goiters show hyperplasia, colloid accumulation, and nodularity. Nodular hyperplasia is commonly seen in multinodular goiter. Cytologic findings include benign appearing follicular cells, abundant colloid, macrophages, and, sometimes, Hürthle cells. Inflammatory disorders of the thyroid, such as chronic lymphocytic (Hashimoto) thyroiditis, contain a mixed population of lymphocytes mixed with benign appearing follicular cells. Malignant nodules may be follicular cell in origin, ie, papillary (most common), follicular, Hürthle cell, or anaplastic. They also may be from parafollicular cells, medullary carcinoma or lymphoma, or other categories.
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Patient with a goiter. Prominent side-view outline.
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Thyroid nuclear scan of a patient with a euthyroid goiter showing different projections.
