TSH alone is not sufficient to exclude all patients with a functioning thyroid nodule from undergoing testing to exclude thyroid cancer.

PURPOSE

The purpose of the study was to analyze whether the thyroid-stimulating hormone (TSH) alone avoids tests to exclude malignancy in all patients with functional thyroid nodules (FTN).

METHODS

Sixty-nine patients with FTN on (99m)Tc scintigraphy, radioiodine uptake test (RIU), (99m)Tc thyroid uptake, TSH assay, T3, and T4 obtained within 48 h were retrospectively identified out of 2,356 thyroid scans performed from January 2000 to April 2007. FTNs were classified as causing total, partial, or no inhibition of the thyroid as group 1, 2, or 3, respectively.

RESULTS

TSH was subnormal in 21 of 69 (30.43%) patients. In group 1 (N = 23, 33.3%), TSH was subnormal, normal, and high in eight, nine, and six patients; in group 2 (N = 17, 24.6%), TSH was subnormal, normal, and high in four, six, and seven patients, and in group 3 (N = 29, 42%), TSH was subnormal, normal, and high in 9, 13, and 7 patients, respectively. TSH was significantly lower in group 1. In T3, T4, (99m)Tc thyroid uptake, and RIU, there were no differences between the three groups.

CONCLUSIONS

Only 30.43% of patients had subnormal TSH. TSH alone cannot avoid tests to exclude malignancy in all patients with FTN. FTN existence can only be accurately assessed by thyroid scintigraphy. The current incidence of FTN may be unknown because scintigraphy is not routinely performed in all patients with thyroid nodules. Thyroid scintigraphy of patients with high TSH can detect diseases such as Hashimoto's thyroiditis and identify patients with FTN in whom no further diagnostic procedures would be needed in patients with normal TSH levels with nondiagnostic fine-needle aspiration results.