Ecdysterone and Nandrolone Interaction: Avoid | Peptide Database

Join others researching Tamoxifen — share findings, ask questions, and learn from real experiences Tamoxifen is a first-generation selective estrogen receptor modulator (SERM) that has been in clinical use since the 1970s. It is FDA-approved for the treatment and prevention of estrogen receptor-positive breast cancer and remains one of the most widely prescribed cancer therapies worldwide. In the context of performance enhancement, tamoxifen is used extensively for post-cycle therapy (PCT) to restore the hypothalamic-pituitary-testicular axis after suppression from anabolic steroids, and for on-cycle gynecomastia prevention by blocking estrogen receptors in breast tissue. Tamoxifen acts as an estrogen antagonist in breast and hypothalamic tissue while functioning as a partial estrogen agonist in bone, the uterus, and the cardiovascular system. Its active metabolite endoxifen, produced via CYP2D6 metabolism, is responsible for much of its pharmacological activity. Tamoxifen competitively binds to estrogen receptors (primarily ERalpha) and exerts tissue-selective effects depending on the local coactivator and corepressor environment. In breast tissue and the hypothalamus, tamoxifen acts as an estrogen antagonist, blocking estradiol-mediated signaling. At the hypothalamus and anterior pituitary, this antagonism removes estrogen-driven negative feedback on GnRH secretion, leading to increased pulsatile GnRH release and subsequent elevation of luteinizing hormone (LH) and follicle-stimulating hormone (FSH). The rise in LH stimulates Leydig cell testosterone production, which is the basis for its use in post-cycle therapy. In bone tissue, tamoxifen acts as a partial estrogen agonist, providing a protective effect on bone mineral density. Tamoxifen is a prodrug that requires hepatic metabolism via CYP3A4 and CYP2D6 to generate its active metabolites, particularly endoxifen, which has approximately 100-fold greater affinity for the estrogen receptor than the parent compound.

Protects blood vessels from age-related deterioration through gene expression regulation. Limits development of atherosclerotic plaques in blood vessels. Decreases endothelial dysfunction that contributes to cardiovascular disease. Regulates sirtuin 1 levels, mimicking some benefits of calorie restriction. Enhances mesenchymal stem cell proliferation and reduces senescence. Reverses senescence-associated secretory phenotype in aging cells.