EFFECT OF L-THYROXINE ADMINISTRATION ON ANTITHYROID ANTIBODY-LEVELS, LIPID PROFILE, AND THYROID VOLUME IN PATIENTS WITH HASHIMOTOS-THYROIDITIS

The changes in the serum thyroid autoantibodies, antithyroglobulin (Tg Ab) and antithyroid-peroxidase (TPOAb), lipid profile, and thyroid vol ume following L-thyroxine (L-T-4) therapy is still a controversial mat ter. We studied 23 patients with goiter due to Hashimoto's thyroiditis ; 10 had clinical hypothyroidism (CH) and 13 had subclinical hypothyro idism (SH). Both groups received L-T-4 (2.0 to 2.5 mu g/kg/day) for a median period of 6 months. Serum concentration of TgAb (normal value: <200 mUI/mL) and TPOAb (normal value: <150 mUI/mL) were measured by a sensitive IRMA using I-125 protein-A. Thyroid volume was determined by ultrasound (normal value: 8-14 mt). At the end of the observation per iod the median serum TSH concentration decreased significantly in both groups (42.9 to 0.55 in CH and 2.4 to 0.74 mU/L in SH patients) and s erum FT4I levels increased only in the CH group (0.87 to 2.1; p < 0.05 ). Serum TgAb concentration did not change in SH patients (72 to 218 m UI/mL) but declined in CH patients (364.5 to 75 mUI/mL; p < 0.05). TPO Ab levels also fell in the CH group (871 to 194 mUI/mL; p < 0.05) and no significant change was noted in SH patients (260 to 116 mUI/mL). Fu rther, a significant correlation was obtained between TSH and either T POAb concentration (r(s) = 0.569, p < 0.01) or thyroid volume (r(s) = 0.488, p < 0.05) in the CH group but not in SH patients (r(s) = 0.232, NS). LDL-cholesterol was higher in the CH (159.4 mg/dL) compared with the SH group (116 mg/dL). Moreover, only in the CH patients was there a significant fall in total cholesterol (224.5 to 165.5 mg/dL, p < 0. 05) and in LDL-cholesterol (159.4 to 104.3 mg/dL, p < 0.05) values. Th e thyroid volume decreased in all patients with CH and in 77% (10/13) of SH patients and a significant median in the thyroid volume decrease was found (39.7% of initial volume in the CH group and 80.9% in SH pa tients; p < 0.01). The influence of L-T-4 on both thyroid autoantibody levels and thyroid volume might be explained by reduction of antigeni c substance through a decreased stimulation of thyroid tissue by circu lating TSH as was seen in CH but not in SH patients. The benefits of t he administration of L-T-4 replacement therapy in SH patients due to H ashimoto's thyroiditis remain to be clarified.