Background: To investigate the long-term effects of supraphysiological, TSH suppressive doses of levothyroxine (TSDL) on bone mineral density (BMD) in patients with affective disorders during an average treatment duration of 69 months.
Methods: In 22 patients, BMD of the spine (lumbar vertebrae L1-4) and femur (femoral neck) was measured by dual energy X-ray absorptiometry (DXA). Forty (40) measurements from the prior study and 48 new follow-up measurements were included. BMD was expressed as Z-scores as a population standard reference. We used a linear mixed model to investigate the duration of TSDL as an explanatory factor for change in BMD compared to an age and gender matched reference population.
Results: We found no significant differences in bone loss between the study and the reference population. The estimated non-significant decrease in Z-score compared to the reference population found was: a) lumbar spine (L1-4): -0.00069/month (p=0.9759) b) neck region of femur: -0.01405/month (p=0.4436). We did not find the factors age, thyroxine-dose or postmenopausal state as predictors for a decline in BMD.
Limitations: Small sample size, no bone density assessment prior to treatment with TSDL, no patient control group with mood disorders who did not receive TSDL, variable bone density follow-up intervals.
Conclusion: This study did not demonstrate evidence that long-term treatment of affectively ill patients with TSDL accelerates loss of BMD compared to an age- and gender-matched reference population.
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