Bone Metabolism in Patients with Differentiated Thyroid Carcinoma Receiving Suppressive Levothyroxine Treatment

Aim: Patients with differentiated thyroid carcinoma (DTC) must receive suppressive levothyroxine (LT4) therapy for the rest of their lives. The literature, however, presents conflicting results on how this affects bone metabolism. The aim of this study was to assess the influence of the estrogen status and LT4 therapy, in particular LT4 dosage in micrograms per kilograms (μg/kg), on bone metabolism in female patients with DTC. Material and Methods: Three markers of bone metabolism (C-terminal telopeptide of type I collagen in serum [SCTx]; N-terminal telopeptide of type I collagen in urine [U-NTx]; and osteocalcin [OC]) were investigated in four groups: group REF (healthy premenopausal female controls), group DTC-ES (premenopausal women with DTC and normal estrogen levels), group DTC-ED (postmenopausal women with DTC and estrogen deficiency), and group DTC-HRT (postmenopausal women with DTC undergoing hormone replacement therapy [HRT]). All patients with DTC were on a well-adjusted suppressive LT4 therapy...