Efficacy of thyroxine-suppressive therapy and its relation to serum thyroglobulin levels in solitary nontoxic thyroid nodules
Kuo, S.W.; Hu, C.A.; Pei, D.; Ni, K.B.; Shian, L.R.
Journal of the Formosan Medical Association 92(1): 55-60
1993
ISSN/ISBN: 0929-6646 PMID: 8099828 Document Number: 414618
Patients with nontoxic thyroid nodules are often treated with thyroxine (T-4) in order to reduce the size of the nodule, but the efficacy of thyrotropin-suppressive therapy with thyroxine remains uncertain. In this study, 35 patients with a solitary thyroid nodule were given thyroxine (0.1 mg/day) for three months. High resolution (7.5 MHz) sonography was used to measure the size of the nodules before and after thyroxine therapy. The volume of the nodules in 12 patients (34.3%, responders) decreased by more than 50% after thyroxine therapy. In this group, the mean serum thyroglobulin (Tg) level decreased significantly (from 424 to 107 ng/mL, p lt 0.0091). In the nonresponders, the mean serum Tg level did not change significantly after thyroxine therapy (291 vs 261 ng/mL, p gt 0.05). The mean serum total T-4 and free T-4 concentrations increased significantly in both groups after thyroxine therapy (p lt 0.01), the serum total triiodothyronine (T-3) level did not change (p gt 0.05), and the serum thyrotropin level (TSH) and T-3/T-4 ratio decreased markedly (p lt 0.01). Other results disclosed that: (1) nodule volume was significantly correlated with serum Tg concentration (r = 0.65, p lt 0.01), but not with the serum TSH level (p gt 0.05); (2) no significant correlation between the serum Tg level and the TSH level or the T-3/T-4 ratio (p gt 0.05) was observed; (3) the reduction in thyroid nodule volume (%) after thyroxine therapy was significantly correlated with the serum Tg concentration (r = 0.43, p lt 0.05); and (4) the reduction in the volume of the thyroid nodule (%) after T-4 therapy was associated with a younger age, a short duration of nodule presence and a high serum Tg level (p lt 0.05), but not with a patient's sex, body mass index (BMI = body weight in kg/body height in meter-2), serum T-3, T-4, TSH or free T-4 levels, the T-3/T-4 ratio, nodule volume before thyroxine therapy or location of nodule. Thyroxine therapy appears to be a useful tool in reducing nodule size in some patients with solitary thyroid nodules, and patients with a high serum Tg level generally respond better to thyroxine-suppressive therapy.