Risks of estrogen only versus combination HRT
Hormone replacement therapy (HRT) is used to help relieve symptoms of menopause by replacing female hormones that the body has stopped making naturally. Most widely used forms of HRT are estrogen only and can be used by women with or without a uterus. However, postmenopausal women who have not had a hysterectomy may be at risk of endometrial cancer after long-term HRT, due to continued action of oestrogen on the endometrium.
Oestrogen stimulates growth and proliferation of the endometrium and without the normal hormonal balance provided by progesterone, this stimulation by oestrogen can lead to excessive proliferation of the endometrial cells or endometrial hyperplasia, which increases risk of endometrial carcinoma. The addition of a progestogen (natural or synthesised progesterone) counteracts the stimulatory effect of oestrogen, acting in a similar way to natural progesterone.
However, there is some evidence that oestrogen plus progestin can increase risk of breast cancer and ovarian cancer. With more published studies more evidence is available to assess the relative risks of various forms of HRT.1-3
Opinion regarding Oestrogen only HRT are also changing and it is now thought that Oestrogen only HRT does not increase risk of breast cancer or substantially interfere with breast cancer detection by mammography. 3
Types of combination HRT
Combination HRT is available as tablets comprising combination of various forms of Oestrogen and progestin, including:
- Conjugated Oestrogens and Medroxyprogesterone
- Oestradiol and Norethisterone
- Campagnoli C, Clavel-Chapelon F, Kaaks R, Peris C, Berrino F. Progestins and progesterone in hormone replacement therapy and the risk of breast cancer. J Steroid Biochem Mol Biol 2005: 96; 95-108.
- Chlebowski RT, Manson JE, Anderson GL, Cauley JA, Aragaki AK, Stefanick ML, Lane DS, Johnson KC, Wactawski-Wende J, Chen C, Qi L, Yasmeen S,Newcomb PA, Prentice RL. Estrogen plus progestin and breast cancer incidence and mortality in the Women's Health Initiative Observational Study. J Natl Cancer Inst. 2013: 105; 526-35.
- Chlebowski RT andGarnet L. Anderson GL. Changing Concepts: Menopausal Hormone Therapy and Breast Cancer. J Natl Cancer Inst. 2012: 104; 517-27.