Estrogen appears to directly influence bone turnover. Its mechanism is byacting on estrogen receptors in bone cells (1). The hormone influencesvitamin D metabolism by increasing conversion of 25-hydroxyvitamin D(25OHD) to 1,25-(0H)2D as it does in birds (2).
The increase of 1,25-(0H)2D then enhances calcium absorption in the bones(2). Estrogen, thereby, contributes to bone density by slowing down boneloss and its absence can lead to lower bone density and predispose forosteoporosis (1;2).
This biochemistry supports evidence that already exists that estrogenreplacement therapy (ERT) combined with adequate calcium and vitamin Dintake as well as exercise may help prevent osteoporosis (3;4).
Despite the effects, however, I have the same opinion about using long-term estrogen replacement therapy (ERT) in postmenopausal women for osteoporosis as I do about estrogen for reducing risk of cardiovascular disease in postmenopausal women.
While there are benefits outlined suggesting that future research on long-term estrogen therapy is merited, the side risks involved may be too serious for estrogen for prescription at this time. Side risks, which include higher risk of breast cancer and other cancers, generally outweigh benefits of ERT.
Short-term ERT, however, may have its place. According to WebMD and Women's Health Initiative authors and those of WebMD, short-term ERT in low doses may reduce or eliminate risks associated with long-term ERT (5;6). More research is needed to explore use of short-term ERT.
1. Shils ME, Shike M, Ross AC, Caballero B, Cousins RJ. Modern Nutritionin Health and Disease. Baltimore, MD: Lippincott Williams & Wilkins, 2009.
2. Gallagher JC, Riggs BL, DeLuca HF. Effect of estrogen on calciumabsorption and serum vitamin D metabolites in postmenopausal osteoporosis.J Clin Endocrinol Metab 1980;51:1359-64.
3. Gallagher JC, Fowler SE, Detter JR, Sherman SS. Combination treatmentwith estrogen and calcitriol in the prevention of age-related bone loss. JClin Endocrinol Metab 2001;86:3618-28.
4. Gallagher JC. Role of estrogens in the management of postmenopausalbone loss. Rheum Dis Clin North Am 2001;27:143-62.
5. Banks E, Canfell K. Invited Commentary: Hormone therapy risks and benefits--The Women's Health Initiative findings and the postmenopausal estrogen timing hypothesis. Am J Epidemiol 2009;170:24-8.
6. WebMD. Women's Health Initiative (WHI): Risks and benefits of hormone replacement therapy (HRT) and estrogen replacement therapy (ERT). Available at: http://www.webmd.com/hw-popup/womens-health-initiative-whi-risks-and-benefits-of-hormone-replacement-therapy-hrt-and-estrogen.