REFINED USE OF SCINTIGRAPHY IN THE EVALUATION OF NODULAR THYROID-DISEASE

Background. Scintigraphy has been advocated in patients with a thyroid nodule when fine needle aspiration biopsy (FNAB) is not definitive. T he purpose of this study was to determine the incidence of hyperfuncti oning nodules in patients without a definitive FNAB, the correlation o f serum thyrotropin (TSH) levels with the functional status of a nodul e, and whether a sensitive TSH assay can be used in lieu of scintigrap hy. Methods. From 1990 to 1996, patients with a thyroid nodule were ev aluated with FNAB and serum TSH measurement. Iodine-223 scintigraphy w as reserved for patients without a definitive FNAB and was correlated with TSH levels. Results. Of 356 patients with a thyroid nodule, 102 d id not have a definitive FNAB. A hyperfunctioning nodule was diagnosed in 14 of the 102 patients. A low TSH level was detected in 12 (86%) o f 14 patients with a hyperfunctioning nodule (mean = 0.04 +/- 0.38 mu IU/mL) and only 20 (23%) of 88 patients with a hypofunctioning nodule (mean = 0.87 +/- 4.11 mu IU/mL) (P < .05). Only 2 of 70 (2.8%) patient s with a normal or increased TSH level had a hyperfunctioning nodule. Conclusions. A 14% incidence of hyperfunctioning nodules in patients w ithout a definitive FNAB warrants the use of scintigraphy but only whe n serum TSH levels are low, thus avoiding unnecessary scans in 91% of patients with a thyroid nodule.