Endocrine Abstracts

Purpose: Thyrotoxic patients have an increased bone turnover and decreased Bone Mineral Density (BMD) at diagnosis. During antithyroid drug treatment (ATD) the patients improved their BMD but earlier studies have not been able to determine if BMD normalize or how long it will take.

Methods: We have prospectively examined 32 females (approved by Danish Ethical Committee) with newly diagnosed Graves’ disease (antilog10, mean age (CI 95%)): 39 years (34–45) and as controls 20 females with Hashimoto’s thyroiditis (42 years (35–49)) and 20 healthy females without thyroid disease (43 years (38–50)). There were no significant differences between age, weight or height between the 3 groups. We measured T-scores of BMD and BMC by DEXA scans (Norland, XR-26 MarkII/HS) and PTH, Ca²⁺, total and free T3 and T4, TSH, TSH-receptor autoantibodies (TSAb), anti-TPO and lipid profile at baseline and after 3 and 18 months of treatment with thiamazole (Thycapzol^®) and after additionally 21 months follow-up without ATD.

Results: Graves’ patients had a significantly lower BMD (0.928 g/cm² (0.880–0.970)) compared to the Hashimoto patients (1.016 (0.975–1.059)) and the healthy controls (1.017 (0.976–1.060)) (P<0.01). After thirty-nine months follow-up there were no significant differences between the 3 groups for BMD of the spine, hip or total body. In addition, T-scores (columna) were for Graves’ patients, Hashimoto patients and normal controls: −0.2 (−1.2–0.8), −0.4 (−0.9–0.1) and +0.1 (−0.5–0.9), respectively. Compared to baseline, BMD (total body) increased significantly from 0.928 g/cm² (0.880–0.970) to 0.998 g/cm² (0.964–1.034) (P<0.02) in the Graves’ patient. A multiple regression analysis was performed and for the Graves’ patients the strongest predictors for BMD were T3 (B=0.29, P<0.01) and anti-TPO (B=−0.21, P<0.03) and for BMC T3 (B=1.18, P<0.03). The strongest predictor for BMD and BMC for the control group was TSH (B=−0.61, P<0.01 and B=−0.45, P<0.05).

Conclusion: This study showed that thyroid patients are still osteopenic 39 months after initiation of ATD, and we therefore suggest regularly DEXA scans to detect development of osteoporosis after thyrotoxicosis.