Tamoxifen reduces bone turnover and prevents lumbar spine and proximal femoral bone loss in early postmenopausal women.

Although widely used for its anti-estrogen properties tamoxifen has estrogen like effects on a number of tissues including bone and liver. Previous studies suggest a preservation of lumbar spine density in postmenopausal women but the effect on the hip had not been addressed. To determine whether tamoxifen prevents bone loss in the early postmenopausal period bone mineral density at the lumbar spine and femoral neck was measured using dual energy X-ray absorptiometry at presentation and 6 monthly thereafter for 1 year in a prospective controlled study. Also indices of bone turnover, serum osteocalcin and urinary hydroxyproline excretion, were assessed. Fifteen early postmenopausal women with Stage I or II breast cancer treated with tamoxifen and 21 normal postmenopausal women were studied. Sex hormone binding globulin and antithrombin III levels in serum were also measured as indices of the hepatic estrogenic activity. Tamoxifen (20 mg daily) prevented bone loss at the femoral neck and lumbar spine. Median rates of change in bone mineral density (%/year) for the tamoxifen group were +0.09%/year in the lumbar spine and 1.4%/year in the femoral neck compared with -2.3%/year and -1.8%/year for the control group (P = 0.04 and 0.03, respectively). Tamoxifen resulted in a significant decrease in both serum osteocalcin and urinary hydroxyproline by 6 months of treatment and this effect persisted for the 12 months of observation. An increase in sex hormone binding globulin and a decline in antithrombin III levels was also observed. These data indicate that, in recently, postmenopausal women tamoxifen prevented bone loss at both the lumbar spine and femur and reduced bone turnover.