Oestrogen-like effects of tamoxifen on the concentration of proteins in plasma.

The concentrations of 11 plasma proteins were determined by electroimmunoassay in 6 female and one male patient before and after treatment for 1-4 months with tamoxifen (30 mg/day) for advanced cancer. The concentrations of transcortin, sex hormone binding globulin, pregnancy zone protein, apolipoprotein AI and thyroxine binding globulin increased significantly. The concentrations of orosomucoid and haptoglobin decreased significantly. The concentration of albumin, transferrin, prealbumin and retinol-binding protein showed no significant change. The changes after treatment with tamoxifen were thus similar to those which occur after the administration of oestrogens or during pregnancy although they were quantitatively less pronounced. There were also differences in the pattern of change between treatment with tamoxifen and during pregnancy. There was no apparent relationship between response to treatment and changes in concentration of plasma proteins.