ABSTRACT
OBJECTIVE: To evaluate the various effects of hormone replacement therapy (HRT) on bone mineral density (BMD) for 4 years in postmenopausal women and to compare the characteristics of non-responders to HRT. METHODS: A total of 100 postmenopausal women have been treated with HRT or estrogen replacement therapy for 4 years. Spinal BMD was measured by dual energy X-ray absorptiometry. RESULTS: The mean age and menopausal age of the study subjects was 53.3+/-3.6 and 4.7+/-4.0 years. According to the baseline BMD, 32 and 9 women were osteopenic and osteoporotic. Compared with the baseline value, the lumbar BMD increased significantly after one and two years of HRT, but after three years the rate of increment has slowed. However, the change of BMD has significantly increased again after four years of HRT (3.98%, 5.36%, 5.41%, 6.16%, in each year, respectively). Women with baseline osteopenia and osteoporotis gained significantly more BMD after 1 year of HRT than women with baseline normal BMD (p=0.02). There were no significant differences of BMD changes among the 3 treatment regimens (continuous combined, cyclic combined, and estrogen only). After 1 year of HRT, 14 non-responders were indentified who had reduced BMD (-1.7+/-1.6%) compared with baseline BMD whereas 86 responders had increased BMD (4.9+/-4.1%). In the non-responder, BMD increased in two year of HRT but decreased in the three and four year of HRT while BMD increased in the two, three and four year of HRT in responders. After 4 years of HRT, 17 nonresponders (-3.0%+/-1.8%) and 83 responders (8.2+/-7.1%) were indentified. There was no significant difference in age, year since menopause, body mass index and baseline BMD between non-responders and responders. However, non-responders loose their BMD after 1 and 4 year of HRT. CONCLUSION: After HRT, the BMD increased not only first and second year but also fourth year of treatment. The BMD changes did not different according to the treatment regimens. The lower the women's baseline BMD, the greater the BMD increase after HRT. After four years of HRT, 17% of women lose their BMD compared to baseline BMD. The BMD changes in the first year of HRT may be an important predictive factor for the long-term BMD response to HRT in postmenopausal women.