Role of low levels of endogenous estrogen in regulation of bone resorption in late postmenopausal women

J Bone Miner Res. 2002 Jan;17(1):172-8. doi: 10.1359/jbmr.2002.17.1.172.

Abstract

Although median levels of bone turnover are increased in postmenopausal women, it is unclear whether the low circulating levels of endogenous estrogen exert a regulatory role on these levels. This issue was evaluated by assessing the effect of a blockade of estrogen synthesis on bone turnover markers in 42 normal women (mean age +/- SD, 69 +/- 5 years) randomly assigned to groups receiving the potent aromatase inhibitor letrozole or placebo for 6 months. Letrozole treatment reduced serum estrone (E1) and estradiol (E2) to near undetectable levels (p < 0.0001). This treatment did not affect bone formation markers but, as compared with the placebo group, increased bone resorption markers (urine 24-h pyridinoline [PYD] by 13.3% [p < 0.05] and 24-h urine deoxypyridinoline [DPD] by 14.2% [p < 0.05]) and decreased serum parathyroid hormone (PTH) by 22% (p = 0.002). These data indicate that in late postmenopausal women even the low serum estrogen levels present exert a restraining effect on bone turnover and support the concept that variations in these low levels may contribute to differences in their rate of bone loss.

Publication types

  • Clinical Trial
  • Randomized Controlled Trial
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Aged
  • Aromatase Inhibitors
  • Bone Remodeling / drug effects
  • Bone Remodeling / physiology
  • Bone Resorption / blood*
  • Bone Resorption / chemically induced
  • Double-Blind Method
  • Enzyme Inhibitors / pharmacology
  • Estradiol / blood
  • Estrogens / blood*
  • Estrone / blood
  • Female
  • Humans
  • Letrozole
  • Menopause / blood
  • Middle Aged
  • Nitriles / pharmacology
  • Osteoporosis, Postmenopausal / blood
  • Prospective Studies
  • Triazoles / pharmacology

Substances

  • Aromatase Inhibitors
  • Enzyme Inhibitors
  • Estrogens
  • Nitriles
  • Triazoles
  • Estrone
  • Estradiol
  • Letrozole