Bone mineral density in pre-and post-menopausal women with affective disorder treated with long-term L-thyroxine augmentation.

Background: Augmentation with TSH-suppressive L-thyroxine (T4) has been shown to improve the course of illness in otherwise refractory affective disorders. This collaborative study investigates whether T4 augmentation for a minimum of 12 months decreases bone mineral density (BMD) in 26 pre- and post-menopausal women with affective disorder.

Methods: We measured BMD at the femoral neck, Ward's triangle, trochanter and lumbar vertebrae (L1-L4) in 13 premenopausal and 13 postmenopausal women with affective disorder using dual energy X-ray absorptiometry. BMD was expressed as g/cm(2) and as a Z-score, calculated using bone density data from the international reference population standard.

Results: The Z-scores for the pre- and post-menopausal women were within the reference range of the age and sex matched population standard. BMD for the composite group also did not differ either from the population standard. BMD in the lumbar spine and hip did not differ significantly between the pre- and post-menopausal groups. However, there were a relatively high number of postmenopausal patients with BMDs one S.D. lower than the population standard.

Limitations: This is a cross-sectional study with a relatively small sample size.

Conclusions: The study demonstrates that T4 augmentation treatment does not reduce BMD to a clinically significant degree in many women with affective disorder. However, the resilience of bone structure to T4 treatment may vary with site and menopausal status. This study underscores the need for regular assessment of BMD during adjunctive thyroid treatments for affective disorder, especially in postmenopausal women.