Aim: To compare the effects of tamoxifen and megestrol acetate on liver proteins, androgens, and glucocorticoids during adjuvant treatment for postmenopausal breast cancer.
Methods: A subgroup of women within a large prospective multicenter trial were followed with blood sampling every 3 mo during 2 yr. Women were randomized to receive either continuous tamoxifen 40 mg/d or repeated sequential treatment with tamoxifen and megestrol acetate (MA) 160 mg/d.
Results: We found profound and distinct differences between the two regimens. Tamoxifen increased steroid-binding proteins (SHBG and CBG) and suppressed circulating androgens and IGF-I. In contrast, the metabolic effects of tamoxifen were clearly antagonized by MA. There was a rise in IGF-I and marked suppression of steroid-binding proteins. Levels of free testosterone were reduced by 70%. MA also caused apparent adrenal suppression.
Conclusion: The different effects on anabolic/catabolic balance and adrenal function may relate to certain clinical effects during treatment.
Postmenopausal breast cancer adjuvant treatment endocrine effects metabolic effects tamoxifen megestrol acetate
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