Changes in Bone Mineral Density Following Levothyroxine Therapy in Hypothyroidism – A Prospective, Observational Study

Background/Objective: Thyroid hormones play a significant role in skeletal metabolism and bone turnover.We investigated the effect of levothyroxine (LT4) replacement on bone mineral density (BMD) using dual-energy X-ray absorptiometry (DEXA) in newly diagnosed patients with hypothyroidism. Methods:In this prospective, observational study, we included 70 adult patients newly diagnosed with either overt (OH) or subclinical hypothyroidism (SCH).LT4 was initiated at 1.6 g/kg/day and 25 g/day in OH and SCH, respectively, and the dose was adjusted every two months to achieve euthyroidism.BMD was done at baseline and two months after attaining euthyroidism.The results were analysed using appropriate statistical methods, and a p-value of less than 0.05 was considered significant. Results:The study participants (51F; 19M) had a mean age of 36.6 10.7 years, body weight of 63.5 13.6 kg, and a body mass index of 25.5 4.2 kg/m.A total of 46 (66%) patients had OH, and 24 (34%) patients had SCH.The mean duration of LT4 therapy to achieve euthyroidism was 7.3 2.2 months.The BMC (gm) during hypothyroidism (1828 345.6) changed significantly after achieving euthyroidism (1883 350.8) (p=0.0004).Similar benefit was seen in the Z score of the lumbar spine and femoral neck (p<0.0001). Conclusion:LT4 therapy correlated with change of BMD at the lumbar spine and femoral neck within one year.Further studies involving a bigger sample, long-duration follow-up, along with histomorphometric and fracture data, are required to confirm the findings of our study.