A woman with a history of estrogen receptor-positive breast cancer is prescribed tamoxifen for chemoprevention. Tamoxifen acts as an estrogen agonist at which site, accounting for its associated increased risk of endometrial cancer?

• A Breast tissue
• B Liver
• C Bone
• D Endometrium ✓

Explanation

Tamoxifen is a selective estrogen receptor modulator (SERM) with tissue-specific agonist/antagonist activity. It is an antagonist in breast (therapeutic effect) but a partial agonist in the endometrium, stimulating endometrial proliferation and increasing endometrial cancer risk 2 to 3 fold. This tissue selectivity arises from differential expression of coactivators and corepressors.

Reference: Katzung Basic and Clinical Pharmacology, 15th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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