Effects of tamoxifen on the serum levels of oestrogens and adrenocortical steroids in postmenopausal breast cancer patients.

Peripheral serum levels of cortisol, dehydroepiandrosterone (DHA), dehydroepiandrosterone sulphate (DHA-S), oestradiol-17 beta and total oestrone were measured in 17 postmenopausal breast cancer patients and on age-matched healthy controls. In the breast cancer patients analyses were performed before and after 1, 2, 4, 8 and 12 weeks of treatment with tamoxifen. Basal DHA levels were significantly higher in breast cancer patients than in controls; otherwise no significant differences were noted. Treatment with tamoxifen resulted in significantly elevated levels of cortisol throughout the period of treatment; this effect was probably solely due to an increase in transcortin levels. A transient but significant elevation in total oestrone, probably related to liver function, was observed after one week of treatment. No significant effects of tamoxifen were noted on serum DHA, DHA-S or oestradiol-17 beta. The results indicate that tamoxifen does not affect the adrenocortical steroid biosynthesis in postmenopausal women. The oestrogenic effects of tamoxifen upon FSH, prolactin and the oestrogen induced Pregnancy Zone Protein (PZP) in postmenopausal women, described in a previous communication from this group, are probably not due to any increase in the serum oestrogens since this increase is transient and hardly impressive. The weak oestrogenic effect of the tamoxifen-receptor complex itself may thus be sufficient to produce net oestrogenic effects in subjects with low endogenous oestrogens such as postmenopausal women.