Estrogens activate bone morphogenetic protein-2 gene transcription in mouse mesenchymal stem cells

Exercise and Estrogen or Estrogen Alternatives (Phytoestrogens, Bisphosphonates) for Preservation of Bone Mineral in Postmenopausal Women

Research in animal models indicates that without estrogen, the effectiveness of exercise for increasing bone mineral in females is reduced. With decreased estrogen levels, there is an increase in the threshold at which strains are detected by bone, in turn reducing the transmission of mechanical to biochemical signals for bone formation. Studies combining estrogen replacement and exercise training in postmenopausal women have yielded mixed results but indicate that the combination of interventions may be more effective than either intervention alone for increasing bone mass. Given the continued debate over the risks and benefits of estrogen replacement, other compounds such as bisphosphonates or phytoestrogens may be preferred in combination with exercise training for optimally increasing bone mass and preventing osteoporotic fracture. Studies on animals show that the combination of bisphosphonate or phytoestrogen supplementation with exercise training is effective, but trials in humans are lacking. Key words: osteoporosis, hormone replacement therapy, bisphosphonates, phytoestrogens, isoflavones

Role of cytokines in postmenopausal bone loss

It is increasingly recognized that changes in cytokine activity are involved in the pathophysiology of postmenopausal bone loss in many ways. Estrogen may affect skeletal cytokine activity by diverse mechanisms such as direct interference with cytokine gene transcription, regulation of major signaling molecules, changes in lymphocyte function, and central effects on the hypothalamic-pituitary-adrenal axis. This article summarizes our current knowledge of these interactions and discusses the possible implications with respect to the prevention and treatment of postmenopausal osteoporosis.

A osteoporose e os distúrbios endócrinos da tireóide e das gônadas

Apesar da dedicação incessante dos pesquisadores no estudo da osteoporose, muito ainda necessita ser elucidado. A deficiência dos esteróides sexuais, principalmente a de estrógeno, é considerada a principal causa de osteoporose, embora existam inúmeros outros fatores envolvidos. O hipertireoidismo, por exemplo, é considerado um dos fatores de risco para indução ou agravamento da osteoporose e tem despertado o interesse para o estudo dos efeitos de T3 e T4 sobre o metabolismo ósseo. Embora o hipotireoidismo e a afuncionalidade das gônadas seja uma associação freqüente na mulher, a hipofunção da tireóide não é considerada fator de risco para a osteoporose da menopausa. Assim, o estudo da inter-relação entre os distúrbios endócrinos, tão comuns na idade avançada, e a osteoporose é fundamental, pois deste conhecimento poderão advir meios de controle e tratamento adequados, bem como a definição da real natureza do distúrbio ósseo. O objetivo desta revisão é apresentar e discutir alguns aspectos da osteoporose e sua inter-relação com os distúrbios endócrinos da tireóide e das gônadas.