Effect of block-replacement regimen on bone mineral density and biochemical markers in patients with thyrotoxic bone disease

Intorduction: Abnormal bone metabolism in patients with thyrotoxicosis is well documented, but time-course of recovery remains poorly understood. Objective: To evaluate changes in bone density and bone metabolic parameters in thyrotoxicosis before and after therapy. Methods: Forty patients with thyrotoxicosis (11 males; mean age 35.5 ± 9.9 years) rendered euthyroid with methimazole and maintained on block-replacement therapy were followed up for six months at a tertiary care setting. Of these, 21 had completed follow-up evaluation. Bone mineral density (BMD) at lumbar spine (LS), hip and biochemical markers were estimated before and after therapy. Results: At LS, 21% women and 35% men had a Z score less than –2. At the neck of femur (NOF),17% women and 18% men had Z score less than -2. LS was more severely affected (p 30 ng/mL (>50 nmol/L)]. Serum T 4 correlated negatively with Z-scores at LS, NOF, trochanter and Ward’s area. There was improvement in BMD (p<0.01) and Z scores (p<0.01) at all levels post-treatment with higher increase at NOF (p=0.046). A significant decrease in serum calcium, 24 hour urinary calcium and phosphate and the fractional excretions of calcium and phosphate was also seen, while serum N-tact PTH levels increased.