Endogenous sex hormones and C-reactive protein in healthy postmenopausal women

Background. Oral oestrogen replacement therapy increases levels of C-reactive protein (CRP). CRP is an established strong predictor of cardiovascular events. It is unknown whether endogenous oestrogen levels are associated with CRP. We therefore studied the relationship between endogenous sex hormones and CRP in healthy postmenopausal women emphasizing the role of body composition as peripheral fat is both a main source of oestrogen production after menopause and an endocrine tissue with inflammatory activities. Subjects and methods. The study population comprised 889 women participating in the PROSPECT study, an ongoing population-based cohort study. Information on risk factors was collected by questionnaires and clinical examination. Endogenous sex hormone levels and CRP were measured with double antibody radio immuno assay (RIA) from fasting plasma samples. In this cross-sectional study, associations between risk factors and lnCRP were studied using linear regression models. Results. Increases in oestrone and free oestradiol levels and the free androgen index were related to an increase in lnCRP of 1.19, 1.23 and 1.21 mg dL(-1) respectively. Body mass index (BMI), waist circumference and physical activity were strongly related to CRP levels, independent of age and other cardiovascular risk factors. Levels of all sex steroids but dehydroepiandrostenedione decreased with age. In age-adjusted analyses, an increase in waist circumference or BMI by one quartile was associated with a 1.28-fold and 1.26-fold increase in CRP. The relationship between endogenous hormones and CRP was modestly attenuated but remained highly significant after adjustment for body composition, physical activity and other traditional cardiovascular risk factors. Conclusions. Our findings show that in postmenopausal women high levels of endogenous oestrogenic and androgenic sex steroids coincide with high CRP levels. This was only explained in part by markers of body composition or intra-abdominal fat.