Curbside Consults

VOL 109 / NO 6 / JUNE 2001 / POSTGRADUATE MEDICINE

How to evaluate an enlarged thyroid?

Q: What is the best way to work up an enlarged thyroid?

Family physician, New Mexico

A: Thyroid disease in general and enlarged thyroid (goiter) in particular are common. A systematic, rational approach to assessment of goiter is essential because long-term ramifications can be substantial (1).

Three basic questions need to be addressed in a patient with a goiter: Is there evidence of thyroid dysfunction? Is the goiter malignant? If the goiter is substantial, is there any evidence of obstruction?

In most cases, thyroid function should be assessed with a "sensitive" thyrotropin (sTSH) assay, which is a very specific and sensitive indicator of thyroid function (assuming the patient's pituitary gland is intact). In young patients with a diffuse goiter and a suppressed TSH level, Graves' disease is the most likely diagnosis. In older patients with a nodular goiter and a suppressed TSH level, a toxic multinodular goiter (Plummer's disease) should be considered. Appropriate assessment and evaluation of a suppressed TSH level in a patient with a goiter therefore would include other studies, such as a radioactive iodine uptake test (with or without a thyroid scan) or, if a multinodular gland is suspected, a thyroid ultrasound. The most common cause of an elevated TSH level in a patient with a diffuse goiter is Hashimoto's thyroiditis. Thyroid cancer rarely causes evidence of thyroid dysfunction.

Obtaining a fine-needle aspiration biopsy remains the test of choice to rule out or confirm malignancy in patients with nodular thyroid disease. In elderly patients with a diffuse goiter and normal thyroid function, lymphoma must be ruled out. We do not routinely perform thyroid scanning or ultrasound to detect cancer because these tests are not specific for this purpose. In young patients with hypothyroidism and a diffuse goiter, malignancy is unlikely; thus, whether to obtain a biopsy is largely determined by the clinical setting.

Lastly, the presence or absence of obstruction must be determined. A chest radiograph is useful to identify tracheal stenosis, and an inspiratory flow volume loop test helps to assess for upper airway obstruction. Surgical removal of a large goiter with either esophageal or tracheal obstructive symptoms or stenosis likely will be required.

Michael D. Whitaker, MD
Consultant, Division of Endocrinology
Mayo Clinic Scottsdale, Scottsdale, Arizona

Reference

1. Argueta R, Whitaker M. When a thyroid abnormality is palpable: what it means and what you should do. Postgrad Med 2000;107(1):100-10

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