Which of the following is protective against endometrial cancer?

• A. Combined oral contraceptives
• B. Turner syndrome
• C. Increased estrogen exposure
• D. Tamoxifen use

Answer: (A)

Reducing endometrial exposure to estrogen lowers the risk of endometrial cancer. When estrogen acts on the lining without enough progesterone to oppose it, the endometrium proliferates and can become hyperplastic or malignant over time.

Combined oral contraceptives provide both estrogen and a progestin. The progestin counteracts estrogen’s effect on the endometrium, promoting thinning and shedding of the lining, and they suppress ovulation, which lowers overall estrogen production by the ovaries. This dual action decreases the endometrium’s proliferative stimulus, markedly reducing cancer risk and often for years after stopping the pills.

Tamoxifen, by contrast, can act like estrogen on the endometrium, increasing proliferation and cancer risk. Turner syndrome isn’t something that reliably protects against endometrial cancer; risk is more tied to hormonal exposure patterns than to a specific chromosomal condition.