THYROID NODULES are a common clinical problem. Epidemiologic studies have shown the prevalence of palpable thyroid nodules to be approximately 5% in women and 1% in men living in iodine-sufficient parts of the world (1,2). In contrast, high-resolution ultrasound can detect thyroid nodules in 19%–67% of randomly selected individuals with higher frequencies in women and the elderly (3).

The clinical importance of thyroid nodules rests with the need to exclude thyroid cancer that occurs in 5%–10% depending on age, gender, radiation exposure history, family history, and other factors (4, 5). Differentiated thyroid cancer, which includes papillary and follicular cancer, comprises the vast majority (90%) of all thyroid cancers (6). In the United States, approximately 23,500 cases of differentiated thyroid cancer are diagnosed each year (7), and the yearly incidence may be increasing (8). In 1996, the American Thyroid Association (ATA) published treatment guidelines for patients with thyroid nodules and thyroid cancer (9). Over the last decade, there have been many advances in the diagnosis and therapy of both thyroid nodules and differentiated thyroid cancer.

Controversy exists in many areas, including the most cost-effective approach in the diagnostic evaluation of a thyroid nodule, the extent of surgery for small thyroid cancers, the use of radioactive iodine to ablate remnant tissue after thyroidectomy, the appropriate use of thyroxine suppression therapy, and the role of human recombinant thyrotropin. In recognition of the changes that have taken place in the overall management of these clinically important problems, the ATA appointed a task force to reexamine the current strategies that are used to diagnose and treat thyroid nodules and differentiated thyroid cancer, and to develop clinical guidelines using principles of evidence-based medicine. Members of the taskforce included experts in thyroid nodule and thyroid cancer management with representation by endocrinology, surgery, and nuclear medicine.

Other groups have previously developed guidelines, including the American Association of Clinical Endocrinologists and the American Association of Endocrine Surgeons (10), the British Thyroid Association and The Royal College of Physicians (11), and the National Comprehensive Cancer Network (12), which have provided somewhat conflicting recommendations because of the lack of high-quality evidence from randomized controlled trials.