Changes in plasma concentrations of osteoprotegerin before and after levothyroxine replacement therapy in hypothyroid patients

CONTEXT: Recent study has shown that overt hypothyroidism (oHT) is associated with increased plasma osteoprotegerin (OPG) levels. OBJECTIVE: Our objective was to examine the plasma OPG level alteration before and after levothyroxine (L-T4) treatment in oHT and subclinical hypothyroidism (sHT). PATIENTS: The study subjects included oHT and sHT patients and healthy individuals (20 subjects in each group). METHODS: All patients were given L-T4 therapy to maintain a euthyroid state. Plasma OPG concentration was measured in duplicate by a sandwich ELISA. RESULTS: Plasma OPG levels in oHT and sHT before treatment were significantly higher than levels in controls (P < 0.01). After normalization of thyroid function, OPG levels in both groups decreased markedly (P < 0.01). The absolute changes in OPG showed a significant positive correlation with the changes in TSH (P < 0.05) and negative correlation with the changes in endothelium-dependent arterial dilation (P < 0.01) in hypothyroid patients during the course of treatment. CONCLUSION: OPG may be involved in the development of vascular dysfunction in hypothyroid patients.