Post‐menopausal hormone therapy and concentrations of protein C and antithrombin in elderly women

The effects of post‐menopausal hormone therapy (HRT) on blood coagulation in elderly women are not well defined. We studied associations of HRT use with levels of natural anticoagulant proteins in a cross‐sectional study of 3393 women ≥ 65 years of age participating in the Cardiovascular Health Study. Protein C antigen and antithrombin were measured in all users (n = 230 unopposed oestrogen; 60 oestrogen/progestin) and a comparison group of 196 age‐ and race‐matched non‐users. Compared with non‐users, oestrogen use was associated with higher protein C (4·80 vs. 4·30 µg/ml, P 0·05). In both user groups, antithrombin was lower than in non‐users (109% for each vs. 115% in non‐users, P