Accelerated Bone Degradation in Thyroid Carcinoma Patients during Thyroxine Treatment, Measured by Determination of the Carboxyterminal Telopeptide Region of Type I Collagen in Serum1)

Summary: We studied the effects of long-term suppressive thyroxine treatment on serum markers of bone collagen synthesis and degradation in thyroid carcinoma patients, and the relationship of these effects to the serum concentra-tions of thyrotropin, free thyroxine and free triiodothyronine were investigated. Thirty-seven thyroid carcinoma patients receiving a stable thyroxine dose, and thirty-five controls participated in a cross-sectional study. Bone collagen synthesis and degradation were measured by using specific radioimmunoassays to determine the serum concentrations of carboxyterminal propeptide of type I procollagen, and carboxyterminal telopeptide region of type I collagen, respectively. Serum thyrotropin, free T4 and free T3 were measured by time-resolved fluoroimmunoassays (Delfia®). Serum carboxyterminal telopeptide region of type I collagen concentrations of thyroid carcinoma patients were significantly higher than those of the controls (p = 0.0012). Serum carboxyter-minal propeptide of type I procollagen concentrations did not differ significantly between the patients and controls (p = 0.85). Significant associations between age or physical activity, and carboxyterminal propeptide of type I procollagen or carboxyterminal telopeptide region of type I collagen were found in the controls, but not in the patients. Thyrotropin, free T4 or free T3 were not significantly associated with carboxyterminal propeptide of type I procollagen or carboxyterminal telopeptide region of type I collagen in either the control or patient group. From these results it is concluded that long-term suppressive thyroxine treatment seems to accelerate bone degrada