Reproductive and Post-reproductive Health Quiz

See Tamoxifen and Raloxifene (SERMs). Option C is correct. Tamoxifen is a selective oestrogen receptor modulator (SERM): a drug that binds the oestrogen receptor but acts as an antagonist (a blocker) in some tissues and an agonist (an activator) in others. In breast tissue it is an antagonist: it competes with oestrogen for the receptor, so growth signals that oestrogen would normally give to the cell are reduced. That is the basis for its use in oestrogen-receptor-positive breast cancer (cancer whose cells carry oestrogen receptors and depend on oestrogen to grow). The same drug behaves like an oestrogen in the endometrium and in bone, which is why the tissue matters in the question and why tamoxifen has a different adverse-effect profile from an aromatase inhibitor. The BNF recommends tamoxifen as the initial adjuvant endocrine therapy in premenopausal women and in men with oestrogen-receptor-positive invasive breast cancer. A simple memory aid is that tamoxifen blocks the receptor in the breast, while anastrozole removes the oestrogen supply.

• Drug type: tamoxifen is a selective oestrogen receptor modulator (SERM).
• In breast tissue: it is an antagonist that competes with oestrogen for the receptor.
• Elsewhere: it acts like an oestrogen in the endometrium and bone.
• Use: oestrogen-receptor-positive breast cancer.