THYROID-FUNCTION IN POSTMENOPAUSAL WOMEN WITH BREAST-CANCER ON TAMOXIFEN

In 42 postmenopausal women with breast cancer, aged 48-85 years (mean age 62.4 years) serum thyroid hormone concentrations were measured bef ore and after 6 months of tamoxifen therapy (20 mg daily). In particul ar triiodothyronine (T-3), thyroxine (T-4), free triiodothyronine (FT3 ), free thyroxine (FT4), thyroxine-binding globulin (TBG) and thyroid- stimulating hormone (TSH) concentrations before and 30 minutes after t hyrotrophin-releasing hormone (TRH) administration (200 mu g I. V.) we re measured before and 6 months after tamoxifen therapy.T-3 and T-4 co ncentrations increased significantly (p<0.001 and p<0.05, respectively ) whereas FT3 and FT4 remained unchanged (p>0.05), TBG increased signi ficantly (p<0.001) and basal TSH concentrations as well as TSI-I respo nse to TRH injection increased significantly (p<0.05) after tamoxifen therapy. It is concluded that tamoxifen administration changes thyroid hormone concentrations. However free thyroid hormone levels remain un changed and the patients remain euthyroid after long-term tumoxifen th erapy.