Estrogen exercise effect

McTiernan A, Rajan KB, Ulrich CM et al. (2004) Effect of exercise on serum estrogens in postmenopausal women a 12-month randomized clinical trial. Cancer Res 64 2923-2928... 

Age, calcium intake, hormonal status, exercise and vitamin status have all been implicated in the development of osteoporosis. Estrogen levels represent an important factor in skeletal calcium retention and homeostasis. In therapeutic trials in which post-menopausal women were given daily doses of estrogens, such therapy has been demonstrated to be partially effective in reducing the rate of bone resorption. However, this therapy has the concomitant hazard of endometrial cancer (10). Vitamin D and its hormones have been given considerable attention in the more recent studies. Without adequate dietary and tissue levels of such vitamins, calcium absorption and bone status will be impaired. 

Caution should also be exercised when assaying samples from subjects who are receiving oral contraceptives or estrogen replacement therapy because cross-reacting steroids may cause elevated results. Most notably, cross-reactivity with estrone is as high as 10% for some assays, but much lower (<1%) in others. This is likely due to a difference in the specificity of the antibody used for estradiol. Similar effects have been observed for metabolites conjugated at the 3 position, like estrone-3-sulfate and estrone-3-glucuronide. ... 

If in-vitro assays are to be used for total estrogenic load (as effects have been shown to be additive) and as such as a pre-filter for LC-MS analyses, a better traceability in the results is needed. This can be obtained by the use of certified reference materials and participation in inter-laboratory exercises. Unfortunately, there are no commercially available reference materials (which should be natural samples) to date, nor is there any organization of open regular inter-laboratory exercises, which should be given priority in the future. Thus, there are issues which remain to be solved, but initiatives to solve these problems are on the way, so this is hopefully only a question of time. 

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