title: Neonatal estrogen exposure results in biphasic age-dependent effects on the skeletal development of male mice.
abstract: Peak bone mass, one of the most important predictors for fracture risk later in life, is attained during puberty and adolescence and influenced by neonatal and pubertal sex-specific gonadal hormones and GH-IGF-I secretion patterns. This study examined the effects of brief neonatal estrogen (NE) exposure on growth and skeletal development in C57BL/6J mice. A single injection of 100-μg estradiol or vehicle was administered on the first day of life. Growth parameters were monitored and skeletal phenotyping performed at 16 weeks in female mice and at 4 and 16 weeks in male mice. NE exposure negatively impacted adult femoral length in both sexes, but adult body weight, areal bone density, and bone strength in female mice were unaffected. In contrast, somatic growth was attenuated in estrogen-exposed male mice throughout the study period. At the prepubertal time point, the estrogen-exposed males exhibited higher bone mineral density, cortical volume, and cortical thickness compared with controls. However, by the time of peak bone mass acquisition, the early skeletal findings had reversed; estrogen-exposed mice had lower bone density with reduced cross-sectional area, cortical volume, and cortical thickness, resulting in cortical bones that were less resistant to fracture. NE exposure also resulted in reduced testicular volume and lower circulating IGF-I. Male mice exposed to estrogen on the first day of life experience age-dependent changes in skeletal development. Prepubertal animals experience greater endocortical bone acquisition as a result of estrogen exposure. However, by adulthood, continued developmental changes result in overall reduced skeletal integrity.
authors.affiliation: Department of Pediatrics (K.J.C., D.L.M.), Division of Pediatric Endocrinology, Oregon Health and Science University Doernbecher Children's Hospital, Portland, Oregon 97239; Bone and Mineral Research Unit (E.A.L., R.F.K.), Department of Medicine, Oregon Health and Science University, Portland, Oregon 97239; Pape Pediatric Research Institute (D.L.M.), Oregon Health and Science University, Portland, Oregon 97239; and Portland Veterans Affairs Medical Center (R.F.K.), Portland, Oregon 97239.
authors.forename: Kara J
authors.initials: KJ
authors.lastname: Connelly
authors.forename: Emily A
authors.initials: EA
authors.lastname: Larson
authors.forename: Daniel L
authors.initials: DL
authors.lastname: Marks
authors.forename: Robert F
authors.initials: RF
authors.lastname: Klein
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D001696:Biomechanical Phenomena; D015519:Bone Density / Q000187:drug effects*; D001846:Bone Development / Q000187:drug effects*; D003270:Contraceptive Agents / Q000008:administration & dosage / Q000494:pharmacology; D004958:Estradiol / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000494:pharmacology; D005260:Female; D013006:Growth Hormone / Q000378:metabolism; D007334:Insulin-Like Growth Factor I / Q000235:genetics / Q000378:metabolism; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D012737:Sex Factors
chemical_list: D003270:Contraceptive Agents; C074283:estradiol 3-benzoate; D004958:Estradiol; D007334:Insulin-Like Growth Factor I; D013006:Growth Hormone