Purpose: Following the clinical observation of increased bone loss in perimenopausal women with still adequate serum estrogen levels but progesterone deficiency, long-term cultures of human osteoblasts (HOB) were used to investigate the influence of concentration and cyclicity of progesterone (P) on the proliferation and differentiation of human osteoblasts (HOBs) in the presence or absence of estradiol. Material and Methods: Primary HOBs obtained from non-osteoporotic, perimenopausal women were cultured for 14 and 28 days respectively in medium containing either estradiol at a concentration of 10(-10) M or no estradiol. From day eight on, progesterone (P) was added in concentrations between 10(-6) M and 10(-10) M. The proliferation of HOBs was measured by asssaying hexosaminidase; differentiation was determined by measuring alkaline phosphatase (ALP). Results: Seven days of exposure to physiologic levels of progesterone (6.4 x 10(-7)-10(-9) M) led to a significant increase in ALP concentrations of up to 70% (p = 0.004-0.019), while supraphysiologic progesterone concentration (6.4 x 10(-6) M) showed a significant (50%) reduction of ALP (p = 0.028). After 21 days of P exposure, ALP increased up to 2.7-fold (p = 0.000-0.004) in the physiologic progesterone range, while supraphysiologic concentrations showed a decrease of ALP by 80% (p = 0.03). This effect was independent of pre- or co-treatment with estradiol. Proliferation was also not significantly affected in the absence of estradiol. Conclusion: The effect of progesterone in HOBs from perimenopausal women was dose-dependent for progesterone, independent of estradiol, and reached its peak at concentrations of 10(-9) M progesterone, corresponding to known serum levels in the luteal phase of ovulatory cycles. These results support the concept of an osteoanabolic function of progesterone. Supraphysiologic progesterone concentrations suppressed the differentiation marker ALP in vitro. This could explain the clinical observation of decreased bone density after long-term use of premenopausal depot progestins.     «

Purpose: Following the clinical observation of increased bone loss in perimenopausal women with still adequate serum estrogen levels but progesterone deficiency, long-term cultures of human osteoblasts (HOB) were used to investigate the influence of concentration and cyclicity of progesterone (P) on the proliferation and differentiation of human osteoblasts (HOBs) in the presence or absence of estradiol. Material and Methods: Primary HOBs obtained from non-osteoporotic, perimenopausal women were...     »