Duk-Chul Lee, et al. gen's positive effects on telomere attrition may affect postmenopausal women treated with long- term hormone therapy (HT). The aim of this study was to investigate the influence of long-term HT on telomere attrition. The differences of telomere length in both post- menopausal women taking HT for more than five years and in postmenopausal women without a history of HT were compared to determine the effects of long-term HT. MATERIALS AND METHODS Study population Study subjects were recruited using an adver- tisement from the health promotion center in a women's hospital in Seoul, South Korea. All sub- jects signed an informed consent form approved by the hospital's Ethical Committee. Two groups of study subjects were created on the basis of hormone therapy history: the HT group and the age-matched, non-HT group. The HT group was defined as postmenopausal women ranging in age from 55 to 69 years old who had been taking estrogen (0.625 mg of conjugated equine estrogen or 2 mg of estradiol combined with progesterone) for more than five years. The non-HT group was defined as postmenopausal women ages 55 to 69 years old who had not taken hormone therapy after menopause. Exclusion criteria were high blood pressure (mean systolic blood pressure 150 mmHg or mean diastolic blood pressure 95 mmHg after two consecutive measurements), high fasting blood glucose (>126 mg/dL), abnormal liver func- tion test (AST >35 IU/L, or ALT >35 IU/L), and a medical history of hysterectomy or other illness (hypertension, diabetes mellitus, liver disease). The questionnaire assessed the medical history of the study subjects, and included illness, age at menopause, duration of HT, and vitamin use, as well as lifestyles such as exercise, alcohol inges- tion, and cigarette smoking. Vitamin use was de- fined as daily use of vitamin C, vitamin E, or a multivitamin. Jogging, walking, swimming, cyc- ling, dancing or participating in alternate forms of exercise more than three times a week for at least Yonsei Med J Vol. 46, No. 4, 2005 30 minutes defined the exercise criteria. Alcohol ingestion was defined as the ingestion of alcohol more than one time each week. Smoking was de- fined by current cigarette smoking. Sixty-five post- menopausal women having had HT and 65 age- matched postmenopausal women with no history of HT were eligible for participation in this study after assessing the inclusion and exclusion criteria. The mean duration of HT (± SD) was 8.4 ± 2.3 years. Biochemical assays Biochemical tests were performed on blood samples collected after more than 12 hours of fasting. Venous blood was drawn and centrifuged, and then the serum was immediately frozen in a refrigerator at -80 . Serum levels of blood glu- cose, high-sensitivity C-reactive protein (hs-CRP), total cholesterol, HDL-cholesterol, and triglyce- rides were assayed by enzymatic techniques (Bayer, Tarrytown, NY, USA) using an auto-analyzer ADVIA 1650 (Bayer, Tarrytown, NY, USA). LDL- cholesterol was calculated using a Friedewald formular.17 Estradiol was assayed by electrochemi- luminescence immunoassay using Elecsys 2010 (Roche, Indianapolis, IN, USA). Plasma total antioxidant status (TAS) was measured using a kit supplied by Randox Laboratories (Diamond, Crumlin, UK) following the methods previously described by Re et al.18 Quantitative PCR Relative ratios of telomere repeat copy number to single copy gene number (T/S ratio) in study subjects was compared with a reference DNA obtained from a healthy young female genes were measured by quantitative PCR as previously de- scribed by Cawthon,19 but with the newly revised primer set designed by Cawthon. This new primer set, which has equal Guanine and Cytosine (GC) content and a higher annealing temperature than other published primers, shows improved correla- tion with the relative mean terminal restriction fragment(TRF) lengths (r2= 0.971 vs 0.794, unpub- lished data by Cawthon RM). This study used β- globin as a single copy gene because it enhanced PCR efficiency and reproducibility better than