Changes in Bone Mineral Density Following Levothyroxine Therapy in Hypothyroidism - A Prospective, Observational...

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 in newly diagnosed patients with hypothyroidism.

In this prospective, observational study, we included 70 adult patients newly diagnosed with either overt hypothyroidism (OH) or subclinical hypothyroidism (SCH). LT4 was initiated at 1.6 μg/kg/d and 25 μg/d in OH and SCH, respectively, and the dose was adjusted every 2 months to achieve euthyroidism. BMD was done at baseline and 2 months after attaining euthyroidism. The results were analysed using appropriate statistical methods, and a P-value of less than 0.05 was considered significant.

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/m². 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 bone mineral content (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).

LT4 therapy correlated with change of BMD at the lumbar spine and femoral neck within 1 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.