title: Androgens and estrogens in skeletal sexual dimorphism.
abstract: Bone is an endocrine tissue expressing androgen and estrogen receptors as well as steroid metabolizing enzymes. The bioactivity of circulating sex steroids is modulated by sex hormone-binding globulin and local conversion in bone tissue, for example, from testosterone (T) to estradiol (E2) by aromatase, or to dihydrotestosterone by 5α-reductase enzymes. Our understanding of the structural basis for gender differences in bone strength has advanced considerably over recent years due to increasing use of (high resolution) peripheral computed tomography. These microarchitectural insights form the basis to understand sex steroid influences on male peak bone mass and turnover in cortical vs trabecular bone. Recent studies using Cre/LoxP technology have further refi ned our mechanistic insights from global knockout mice into the direct contributions of sex steroids and their respective nuclear receptors in osteoblasts, osteoclasts, osteocytes, and other cells to male osteoporosis. At the same time, these studies have reinforced the notion that androgen and estrogen defi ciency have both direct and pleiotropic effects via interaction with, for example, insulin-like growth factor 1, inflammation, oxidative stress, central nervous system control of bone metabolism, adaptation to mechanical loading, etc., This review will summarize recent advances on these issues in the fi eld of sex steroid actions in male bone homeostasis.
authors.affiliation: Laboratory of Molecular Endocrinology, Department of Cellular and Molecular Medicine; Gerontology and Geriatrics, Department of Clinical and Experimental Medicine, KU Leuven; Geriatric Medicine, University Hospitals Leuven, Leuven, Belgium.
authors.forename: Michaël
authors.initials: M
authors.lastname: Laurent
authors.forename: Leen
authors.initials: L
authors.lastname: Antonio
authors.forename: Mieke
authors.initials: M
authors.lastname: Sinnesael
authors.forename: Vanessa
authors.initials: V
authors.lastname: Dubois
authors.forename: Evelien
authors.initials: E
authors.lastname: Gielen
authors.forename: Frank
authors.initials: F
authors.lastname: Classens
authors.forename: Dirk
authors.initials: D
authors.lastname: Vanderschueren
mesh_terms: D000728:Androgens / Q000502:physiology*; D015519:Bone Density; D001842:Bone and Bones / Q000502:physiology*; D004967:Estrogens / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D012727:Sex Characteristics
chemical_list: D000728:Androgens; D004967:Estrogens