Answer
In someone with a uterus, unopposed systemic oestrogen can thicken the womb lining and increase endometrial cancer risk; a progestogen reduces that risk.
Sources for this answer
- Conjugated Oestrogens 0.625mg coated tablets — Current selected SmPCemc · Summary of Product Characteristics
General medicine information. Follow the instructions for your own medicine and speak to a pharmacist or clinician about your individual circumstances.