Unopposed oestrogen

V.a.1.1. Oral HRT preparations. For oral therapy, there is a choice between conjugated equine oestrogens purified from urine, synthetic oestro-gens such as ethinyloestradiol and tibolone, and oestradiol itself. In women with an intact uterus, the oestrogen should normally be given in conjunction with a progestagen in order to protect the endometrium from unopposed oestrogenic stimulation. 

Taylor M, Bowen-Simpkins P, Barrington J. Complications of unopposed oestrogen following radical surgery for endometriosis. J Obstet Gynaecol 1999 19(6) 647-8. 

Carcinoma of the endometrium is associated only with unopposed oestrogens, which increase risk by 2-fold during 5 years rising to 7-fold with longer treatment. Because endometrial cancer is uncommon, the absolute risk is about one-tenth that of thromboembolic disease the risk reduces over 5-10 years after stopping treatment. 

Oestrogen inhibits the age-related loss of bone that occurs in most women after menopause. Observational studies have indicated that the use of oestrogen reduces the risk of vertebral fracture by approximately 50% and the risk of hip fracture by 25-30%. Unopposed oestrogen increases by 10-fold the risk of endometrial cancer, which is diminished by added progestogen. Therefore combinations of oestrogen and progestogen are the mainstay of treatment for postmenopausal osteoporosis they inhibit the rapid bone loss that occurs immediately after the menopause and should be continued for 5 years. 

Exposure to unopposed oestrogens is a risk factor for endometrial carcinoma. Unopposed oestrogens should no longer be used to treat postmenopausal symptoms in women who have not had hysterectomy. Excessive fat consumption and overweight [defined as a body-mass index (BMI) of at least 25 kg/m j are important risk factors present in almost 50% of women with endometrial cancer [7,26] (see Table 6.2). 

---