Oestrogen acts in colon cells predominantly through ERβ,14, 15 which exerts proapoptotic and anti-proliferative effects in the colon16 and its expression is reduced in tumour tissue.17, 18 According to an in vivo study, oestrogen treatment was associated with an increase in expression of ERβ in colon tissue,55 supporting a mechanism by which MHT may affect CRC risk. The gene discussed is ESR2; the disease is colorectal carcinoma.