OBJECTIVE: The aim of this study is to determine the changes in circulating T-cell subpopulations, B cells and natural killer cells under continuous combined postmenopausal hormone replacement therapy. Design: Thirty postmenopausal women were administered estradiol valerate 2 mg/d and norethisterone acetate 1 mg/d for three months. Immunophenotyping with flow cytometry was performed before and 3 months after hormone replacement therapy. Setting: University Hospital Patients: Thirty postmenopausal women Intervention: Thirty postmenopausal women were administered estradiol valerate 2 mg/d and norethisterone acetate 1 mg/d for three months. Main outcome measure: T cell subset numbers and activation, B cell and natural killer cell number RESULTS: The mean percentage of T cells (CD3+), cytotoxic T cells (CD8+), helper T cells (CD4+) did not significantly change after 3 months of hormone replacement therapy. The mean pecentage of B (CD19+) cells significantly increased after 3 months of hormone replacement therapy (p=0.01). The mean percentage of active T cell (CD3+HLA-DR+) and natural killer cells (CD16+CD56+CD3-) decreased significantly after 3 months of hormone replacement therapy (p
Keywords: immune system, postmenopausal hormone replacement therapy