Prevention of postmenopausal bone loss with exchange for short-term HRT for 1alpha-hydroxycholecalciferol

The present study investigated bone turnover with exchange of hormone replacement therapy (HRT) by treatment with 1alpha-hydroxycholecalciferol in early postmenopausal women.

Subjects included a total of 75 postmenopausal women between 49 and 59 years of age who visited the Department of Obstetrics and Gynecology at Osaka Medical College Hospital for regular gynecological checkups and menopausal disorder, postmenopausal osteoporosis or hyperlipidemia, and were diagnosed with menopausal disorder or osteopenia. Changes in bone turnover and vertebral bone mineral density (BMD) in 28 patients who had undergone HRT; conjugated equine estrogen 0.625 mg daily and medroxyprogesterone acetate 2.5 mg daily) for at least 2 years and then switched to 1alpha-hydroxycholecalciferol (0.5 microg orally twice daily) and in 26 patients who were observed without drug administration after discontinuation of HRT were compared with those in 37 patients who continued HRT. BMD of the lumbar spine (L2-4) was determined using Dual Energy X-ray Absorptiometry.

While we observed a significant decrease in vertebral bone mass in the HRT-no medication group at 12 months (P=0.049) and 18 months (P=0.013), there was no significant decrease in vertebral bone mass in either the continuous HRT group or the group with change of HRT to 1alpha-hydroxycholecalciferol. In the group with change of HRT to 1alpha-hydroxycholecalciferol, although urinary pyridinoline level increased significantly from the baseline level throughout the study period (P<0.05), serum propeptide of type-1 procollagen (P1CP) level also increased significantly from the baseline level throughout this period (P<0.001). Furthermore, significant increase from the baseline value (P<0.01) was observed in serum osteocalcin level at 6, 12 and 18 months.

These results indicate that switching to 1alpha-hydroxycholecalciferol therapy after short-term HRT increased both bone resorption and bone formation, and permitted maintenance of increase in bone mass due to HRT for at least 18 months, though this switching accelerated bone turnover. This may have occurred because stimulation of bone formation induced by HRT was maintained by 1alpha-hydroxycholecalciferol, though bone turnover was slightly promoted because of withdrawal of HRT. This method was thus found to be very effective in preventing bone loss in patients who have discontinued HRT and are considered relatively contraindicated for use of estrogen.