Effects of Estrogen and Progesterone on Tibia Histomorphometry in Growing Rats

Abstract

The present study was performed to evaluate possible interactions between estrogen and progesterone on peak cancellous bone mass. Ovariectomized (OVX) growing rats were treated with 17beta-estradiol (4.8 microg/day), progesterone (4.8 mg/day), a combination of the two sex steroids, or with vehicle for 14 days beginning 7 days after OVX. The tibiae were removed for histomorphometric analysis of the proximal metaphysis. OVX and growth each resulted in net resorption of cancellous bone at a sampling site adjusted for longitudinal bone growth. Estradiol and progesterone treatment each antagonized bone loss by inhibiting the decrease in trabecular number. Estradiol increased but progesterone had no effect on trabecular thickness. Progesterone did not influence either osteoclast number or the resorption of the pretreatment fluorochrome label. Estradiol reduced osteoclast number and inhibited label resorption, the latter change being accentuated by combination treatment. Estradiol reduced and progesterone enhanced the mineral apposition and bone formation rates. The results indicate that estradiol and progesterone have independent activities on cancellous bone turnover during growth. Whereas estradiol reduced bone turnover, progesterone had a stimulatory effect on bone formation. These findings suggest that progesterone has a role in establishing and maintaining peak cancellous bone volume during growth.

Ovarian control of growth and sexual size dimorphism in a male-larger gecko

“…1D). In mammals, it was shown that progesterone has a stimulatory effect on bone formation in female rats and thus has the potential to influence skeletal growth in vertebrates (Schmidt et al, 2000). Direct testing of the effect of progesterone on female growth in squamates should therefore be pursued in the future.…”

Physical Activity in the Prevention and Amelioration of Osteoporosis in Women

“…[154] Peak tor β (TGFβ). [166] Some hormones, such as esadult level trabecular BMD measured by QCT is trogen, [167] inhibit proliferation of both osteoblasts achieved at the time of cessation of longitudinal and osteoclasts. Other, and sometimes the same, growth and closure of epiphyseal growth zones at hormones and growth factors can stimulate both about age 19 years.…”

“…In conjunction with by adipocytes in proportion to the size of body fat progesterone, estradiol reduces osteoclast activity, mass, [212] is another hormone that plays an important preserves trabecular bone and has overall anabolic role in both bone cell proliferation and differentia-action in bone. [167] Finally, cortisol inhibits osteotion. Leptin is hypothesised to promote longitudinal blast apoptosis.…”

“…[167] cent female athletes. Elite young female athletes It should be noted that the progression of bone have lower body mass, body fat content, and retardcells through the cell cycle is not simply a matter of ed bone and sexual development compared with appropriate hormonal stimulation.…”

Efeito da associação hipotireoidismo-castração no osso e nas paratireóides de ratas adultas

“…Um dos fatores que podem ser apontados para justificar a diferença na intensidade da osteopenia da tíbia em comparação aos demais ossos longos foi o maior crescimento longitudinal desse osso na associação hipotireoidismo-castração, quando comparado ao grupo hipotireóideo não castrado (tabela 3). Essa observação é importante, pois a tíbia é um dos ossos mais utilizados como modelo para os estudos do metabolismo ósseo nas disfunções endócrinas (18,(47)(48)(49). Mas, no presente estudo, ficou claramente demonstrado que a resposta da tíbia às disfunções das gônadas e da tireóide é específica e não segue o mesmo padrão dos demais ossos.…”