A 58-year-old postmenopausal woman completed five years of adjuvant tamoxifen for oestrogen receptor positive breast cancer. She now presents with postmenopausal vaginal bleeding. Endometrial sampling is indicated primarily because tamoxifen:
- A Acts as a pure oestrogen receptor antagonist in all tissues
- B Induces ovarian steroidogenesis even after menopause through FSH receptor sensitisation
- C Behaves as a partial agonist at the endometrium, increasing the risk of endometrial hyperplasia and carcinoma ✓
- D Converts endogenous androgens to oestradiol within the endometrium
Correct answer: C. Behaves as a partial agonist at the endometrium, increasing the risk of endometrial hyperplasia and carcinoma
Explanation
Tamoxifen is a selective oestrogen receptor modulator: it antagonises oestrogen action in breast tissue but acts as a partial agonist in endometrium and bone. Chronic endometrial stimulation raises the incidence of hyperplasia, polyps and endometrial carcinoma, so postmenopausal bleeding on tamoxifen always warrants evaluation. Option D describes the peripheral aromatisation caused by androstenedione in adipose tissue, a physiological pathway unrelated to tamoxifen's receptor pharmacology.
Reference: Katzung Basic and Clinical Pharmacology, 15th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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