The Women's Health Initiative (WHI) trial demonstrated an increased risk of breast cancer with combined (oestrogen + progestogen) HRT. The specific progestogen in the WHI combined arm that carried the breast cancer risk signal was:

• A Micronised progesterone (Utrogestan)
• B Dydrogesterone
• C Norethisterone acetate (NETA)
• D Medroxyprogesterone acetate (MPA) ✓

Explanation

The WHI trial used medroxyprogesterone acetate (MPA) as the progestogen component combined with conjugated equine oestrogen. MPA is a synthetic progestogen with androgenic and glucocorticoid receptor activity, which is associated with greater proliferative effects on breast tissue compared to micronised progesterone. Subsequent observational studies (E3N cohort, CGHFBC meta-analyses) suggest that micronised progesterone and dydrogesterone have a more neutral or lower breast cancer risk profile. This has driven a shift toward 'body-identical' progesterone in modern HRT prescribing in Europe.

Reference: Shaw's Textbook of Gynaecology, 17th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.