Clinical Investigations

Thyroid function is routinely assessed by measuring blood levels of thyroid stimulating hormone (TSH) and, if appropriate, the levels of thyroxine and triiodothyronine in patients with thyroid gland disease, including those with neoplastic conditions. Occasionally calcitonin levels are measured. Elevated plasma thyroglobulin (and calcitonin in medullary thyroid carcinoma) following ablative therapy for malignant disease can indicate recurrence or metastasis. Autoantibodies to thyroglobulin, microsomal antigen and the TSH receptor may also be evaluated.

Ultrasonography is helpful in distinguishing a solitary nodule from a multinodular goitre with a so-called dominant nodule but cannot differentiate benign from malignant disease. Plain radiographs of the neck and chest may demonstrate deviation of the trachea, mediastinal expansion or lymphadenopathy although they are more accurately determined by CT and MRI scanning. Scintiscanning, particularly with Iodine-123 rather than Technetium-99m, can determine the functional status of the tissue. Functioning or "hot" nodules are very unlikely to be malignant.

FNA is the investigation of choice for thyroid enlargement, particularly for solitary nodules in euthyroid patients or when there is a history of a rapidly growing mass with airway obstruction. A definitive diagnosis is often possible with FNA, although the distinction between a cellular colloid nodule, follicular adenoma and a follicular carcinoma is generally impossible.

Assessment of vocal cord function is important in the clinical assessment of patients with goitre; vocal cord paralysis is a sinister finding.

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