OBJECTIVES: Osteoporosis, defined as decreased bone mass and structural deterioration of bone, increases the incidence of fractures. Recently, there have been reports suggesting that thyroid hormones are related to bone mineral density (BMD). It has been reported that low normal circulating thyrotropin (TSH) levels correlate with lower BMD and that thyroxine (T4) and bone density are negatively related. This research aims to examine the relationship between BMD and thyroid diseases and other functional changes in postmenopausal women. METHODS: The medical records of 2,279 postmenopausal women who attended the health care clinic in eight university hospitals between March 2001 and December 2007 were reviewed retrospectively. We determined the baseline characteristics of the women, including age, height, weight, and body mass index (BMI). The BMD was measured by dual-energy X-ray absorptiometry (DEXA). The correlation between the thyroid status and BMD was analyzed using the SPSS 12.0 program. RESULTS: This research used data from a relatively large number of postmenopausal women gathered in a multicenter approach. Of the thyroid functional tests, thyroid stimulating hormone (triiodothyronine or T3) and T4 correlated with BMD, while free T4 and TSH did not show a statistically significant correlation. After adjusted age, thyroid function test did not correlate with BMD. Osteopenia was significantly higher in the group with TSH below 0.5 mU/L compared with groups that had normal or high TSH. There was no statistically significant difference in lumbar BMD and total hip BMD among patients with thyroid diseases and healthy patients. CONCLUSION: The level of T3 and T4 correlated well with BMD in Korean post-menopausal women.