Objective: To study the impact of thyroxine (T4) withdrawal on serum osteoprotegerin concentrations in women, using a healthy euthyroid control group matched for age and postmenopausal status as reference.
Subjects and design: Nineteen women with differentiated thyroid carcinoma were studied the last day on T4 suppressive treatment, 4–7 days after withdrawal and the day before whole body scanning. Eighteen women matched for age and postmenopausal status served as controls. Serum thyroid hormones, urinary bone markers and serum osteoprotegerin concentrations were measured. Statistical methods included repeated measures analysis of variance and one-way analysis of variance.
Results: Patients progressed from subclinical or mild hyperthyroidism at baseline to normal free T4 and triiodothyronine levels 4–7 days later, ending in overt hypothyroidism before scanning. Serum osteoprotegerin increased, and urinary deoxypyridolines/creatinine and pyridolines/creatinine ratios decreased, with acute hypothyroidism (P = 0.026, P = 0.003, and P < 0.001 respectively). Urinary deoxypyridolines/creatinine ratio, pyridolines/creatinine ratio, and serum osteocalcin during hypothyroidism were lower compared with those of healthy controls (P = 0.023, P = 0.019, and P = 0.011 respectively). Serum osteoprotegerin concentrations were higher in postmenopausal patients when compared with premenopausal ones, irrespective of the changes in thyroid function (P = 0.001).
Conclusion: Serum osteoprotegerin concentrations increase following acute hypothyroidism after T4 withdrawal in women with differentiated thyroid carcinoma, and also with postmenopausal status.