Effects of anti-estrogens on bone in castrated and intact female rats

Breast Cancer Res Treat. 1987 Oct;10(1):31-5. doi: 10.1007/BF01806132.


The effects of the antiestrogens tamoxifen and keoxifene on the bone density of intact and ovariectomized female rats were determined after 4 months of therapy. The antiestrogens did not cause a decrease in bone density in intact animals, although uterine wet weight did decrease. Ovariectomy caused an increase in body weight (25%) and a significant decrease in femur density (P less than 0.01). Antiestrogens did not further decrease the bone density of ovariectomized rats but rather helped to maintain bone density. Antiestrogens as well as estrogen (oral estradiol benzoate 25 micrograms daily) helped to maintain bone density in the range observed for the intact rats, but inhibited estrogen stimulation of uterine weight. These contrasting pharmacological actions of antiestrogens suggest that patients receiving long-term adjuvant tamoxifen therapy for breast cancer should be evaluated to determine whether tamoxifen can retard the development of osteoporosis.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Body Weight / drug effects
  • Bone and Bones / analysis
  • Bone and Bones / drug effects*
  • Estradiol / pharmacology
  • Estrogen Antagonists / pharmacology*
  • Female
  • Ovariectomy
  • Piperidines / pharmacology
  • Raloxifene Hydrochloride
  • Rats
  • Rats, Inbred Strains
  • Tamoxifen / pharmacology


  • Estrogen Antagonists
  • Piperidines
  • Tamoxifen
  • Raloxifene Hydrochloride
  • Estradiol