Regulation of adult bone turnover by sex steroids.
Recent reports reveal increasing complexity of mechanisms underlying the bone sparing effects of sex steroids. This review focuses on mechanisms by which sex steroids attenuate endocortical and trabecular adult bone turnover, perhaps their most important property as bone mass regulators. Clearly, estrogen withdrawal increases osteoclast number and bone resorption; however, important open questions are the extent to which osteoblasts and their precursors are involved, and the relative contributions of the RANK/RANKL/OPG system, Fas ligand and Runx2. In addition to reviewing these aspects of estrogen action, we also discuss proskeletal effects of androgens on the adult male skeleton, including aromatization to estrogens and male-specific mechanisms. Detailed understanding of skeletal site- and gender-dependent mechanisms by which sex steroids protect the adult skeleton will provide the foundation for improved risk assessment, prevention and management of osteoporosis.
Frenkel
Baruch
B
Department of Biochemistry and Molecular Biology, Keck School of Medicine, University of Southern California, Los Angeles, California 90033, USA. frenkel@usc.edu
Hong
Albert
A
Baniwal
Sanjeev K
SK
Coetzee
Gerhard A
GA
Ohlsson
Claes
C
Khalid
Omar
O
Gabet
Yankel
Y
D000328:Adult; D000818:Animals; D016723:Bone Remodeling / Q000502:physiology*; D012739:Gonadal Steroid Hormones / Q000378:metabolism*; D006801:Humans; D023421:Models, Animal; D010006:Osteoblasts / Q000166:cytology / Q000378:metabolism; D010010:Osteoclasts / Q000166:cytology / Q000378:metabolism; D013256:Steroids / Q000378:metabolism*
D012739:Gonadal Steroid Hormones; D013256:Steroids