The effects of lithium treatment on bone mineral density in bipolar patients

Background: Lithium is widely used in the treatment and prophylaxis of bipolar disorders. It has been reported that serum calcium and parathyroid hormone (PTH) levels tend to increase in the patients receiving lithium treatment. It is known that parathyroid hormone causes bone resorption. The aim of the present study is to investigate the impact of lithium treatment on the bone mineral density of bipolar patients. Methods: The study group consisted of 15 bipolar patients who have been taking lithium carbonate for at least six months and 15 healty control subjects. Serum samples of the subjects were analyzed for calcium, inorganic phosphorus, free T-3, free T-4, and active parathyroid hormone. Bone mineral density (BMD) of L-2-L-4 vertebrae, femur neck, femur trochanter, and Ward's triangle were measured by Dual X-ray absorptiometry. Results: BMD of the L-2-L-4 vertebrae and femur neck were significantly lower in the study group, when compared with the controls. No statistically significant difference between groups was present in the BMD of Ward's triangle and femur trochanter. Although we found significant negative correlations between duration of lithium treatment and femur neck, spine and Ward's triangle BMDs, duration of illness and spine and Ward's triangle BMDs. Conclusions: This results may support that lithium causes a significant decrease in bone density. We suggest that bone metabolism and bone density monitoring would be appropriate in patients having lithium treatment in order to provide preventive measures when necessary.