Duk-Chul Lee, et al. postmenopausal women who had taken HT than in postmenopausal women without a history of HT. This suggests that long-term hormone ther- apy in postmenopausal women might have the effect of alleviating telomere attrition. Further studies are necessary to more clearly understand the relationship between hormone therapy and telomere attrition. ACKNOWLEDGEMENTS The authors acknowledge Dr. Richard M. Cawthon of the Department of Human Genetics, University of Utah, for his very kind and useful comments on the primer design and quantitative PCR of telomere length. REFERENCES 1. Meyne J, Ratliff RL, Myozis RK. Conservation of the human telomere sequence (TTAGGG)n among verte- brate. Proc Natl Acad Sci USA 1989;86:7049-53. 2. Harley CB, Futcher AB, Greider CW. Telomeres shorten during ageing human fibroblasts. Nature 1990;345:458- 60. 3. Von Zglinicki T, Serra V, Lorenz M, Saretzki G, Lenzen- Grossimlighaus R, Gessner R, et al. Short telomeres in patients with vascular dementia: an indicator of low antioxidative capacity and a possible risk factor? Lab Invest 2000;80:1739-47. 4. Harley CB, Vaziri H, Counter CM, Allsopp RC. The telomere hypothesis of cellular aging. Exp Gerontol 1992;27:375-82. 5. Metcalfe JA, Parkhill J, Campbell L, Stacey M, Biggs P, Byrd PJ, et al. Accelerated telomere shortening in ataxia telangiectasia. Nat Genet 1996;13:350-3. 6. Wyllies FS, Jones CJ, Skinner JW, Haughton MF, Wallis C, Wynford-Thomas D, et al. Telomerase prevents the accelerated cell ageing of Werner syndrome fibroblasts. Nat Genet 2000;24:16-7. 7. Vaziri H, Schachter F, Uchida I, Wei L, Zhu X, Effros R, et al. Loss of telomeric DNA during aging of normal and trisomy 21 human lymphocytes. Am J Hum Genet 1993;52:661-7. 8. Benetos A, Okuda K, Lajemi M, Kimura M, Thomas F, Skurnick J, et al. Telomere length as an indicator of biological aging: the gender effect and relation with pulse pressure and pulse wave velocity. Hypertension 2001;37:381-5. 9. Jeanclos E, Schork NJ, Kyvik KO, Kimura M, Skurnick JH, Aviv A. Telomere length inversely correlates with pulse pressure and is highly familial. Hypertension Yonsei Med J Vol. 46, No. 4, 2005 2000;36:195-200. 10. Panossian LA, Porter VR, Valenzuela HF, Zhu X, Reback E, Masterman D, et al. Telomere shortening in T cells correlates with Alzheimer's disease status. Neurobiol Aging 2003;24:77-84. 11. Cawthon RM, Smith KR, O'Biren E, Sivatchenko A, Kerber RA. Association between telomere length in blood and mortality in people aged 60 years or older. Lancet 2003;361:393-5. 12. Cherif H, Tarry JL, Ozanne SE, Hales CN. Ageing and telomeres: a study into organ-and gender-specific telo- mere shortening. Nucleic Acids Res 2003;31:1576-83. 13. Von Zglinicki T. Oxidative stress shortens telomeres. Trens Biochem Sci 2002;27:339-44. 14. Okuda K, Bardeguez A, Gardner JP, Rodriguez P, Ganesh V, Kimura M, et al. Telomere length in the new born. Pediatr Res 2002;52:377-81. 15. Aviv A. Telomeres, sex, reactive oxygen species, and human cardiovascular aging. J Mol Med 2002;80:689-95. 16. Vasa M, Breitschopf K, Zeiher AM, Dimmeler S. Nitric oxide activates telomerase and delays endothelial cell senescence. Circ Res 2000;87:540-2. 17. Friedewald WT, Levy RI, Fredrikson DS. Estimation of concentration of low-density lipoprotein cholesterol in plasma, without use of preparative ultracentrifuge. Clin Chem 1972;18:499-502. 18. Re R, Pellegrini N, Proteggente A, Pannala A, Yang M, Rice-Evans C. Antioxidant activity applying an im- porved ABTS radical cation decolorization assay. Free Radic Biol Med 1999;26:1231-7. 19. Cawthon RM. Telomere measurement by quantitative PCR. Nucleic Acid Res 2002;30:e47. 20. Von Zglinicki T, Saretzki G, Docke W, Lotze C. Mild hypoxia shortens telomeres and inhibits proliferation of fibroblast: a model for senescence? Exp Cell Res 1995; 220:186-93. 21. Von Zglinicki T, Pilger R, Sitte N. Accumulation of single-stranded breaks is the major cause of telomere shortening in human fibroblasts. Free Radic Biol Med 2000;28:64-74. 22. Petersen S, Saretzki G, von Zglinicki T. Preferential Accumulation of single stranded regions in telomeres of human fibroblasts. Exp Cell Res 1998;239:152-60. 23. Von Zglinicki T. Role of oxidative stress in telomere length regulation and replicative senescence. Ann NY Acad Sci 2000;908:99-110. 24. Serra V, von Zglinicki T, Lorenz M, Saretzki G. Extra- cellular superoxide dismutase is a major antioxidant in human fibroblast and slows telomere shortening. J Biol Chem 2003;278:6824-30. 25. King CM, Bristow-Craig HE, Gillespie ES, Barnett YA. In vivo antioxidant status, DNA damage, mutation and DNA repair capacity in cultured lymphocytes from healthy 75- to 80-year-old humans. Mutat Res 1997;377: 137-47. 26. Mendoza-Nunez VM, Sanchez-Rodriguez MA, Retana- Ugalde R, Vargas-Guadarrama LA, Altamirano-Lozano MA. Total antioxidant levels, gender, and age as risk