Why a woman with a uterus needs a progestogen with HRT
In hormone replacement therapy (HRT), a woman who still has a uterus needs a progestogen (a progesterone-like hormone) with her oestrogen to protect the endometrium (the lining of the womb).
Remember
A woman who still has a uterus must take a progestogen with her oestrogen, because oestrogen alone can make the endometrium overgrow. Oestrogen alone is for women who have had a hysterectomy (removal of the womb).
Memory aid
oestrogen is the accelerator for the womb lining and progesterone is the brake
Use the picture to recall that progesterone opposes oestrogen in the womb lining, and that no womb means no brake is needed.
Oestrogen is the part of HRT that relieves the vasomotor symptoms of the menopause (hot flushes and night sweats). The catch is that oestrogen also stimulates growth of the endometrium, the lining of the womb.
In a woman who still has her uterus, oestrogen given alone is unopposed oestrogen: it acts on the lining without opposition. Over time this overgrowth (endometrial hyperplasia) can progress to cancer. A progestogen, a hormone with progesterone-like action, counteracts this effect, so the lining is protected.
This is why a woman with a uterus is given combined HRT, which contains both hormones. A woman who has had a hysterectomy (removal of the womb) has no endometrium to protect, so oestrogen alone is usually enough for her.
The type of combined HRT depends on her periods. If she is still having periods, she is usually given sequential HRT: the progestogen is added for part of each month, which produces a monthly withdrawal bleed (a period-like bleed when the hormone is stopped). From 12 months without a period, she is usually given continuous combined HRT, which supplies both hormones daily with no scheduled withdrawal bleed.
The protection is for the womb lining only: combined HRT slightly increases the risk of breast cancer.
Key facts
- Oestrogen alone
- in a woman with a uterus it stimulates the endometrium without opposition, which raises the risk of endometrial cancer.
- Combined HRT
- the progestogen protects the womb lining, and the oestrogen treats the symptoms.
- Hysterectomy
- oestrogen alone is recommended, because there is no womb lining to protect.
- Dose, route or timing
- changing the dose, route or timing of oestrogen does not protect the endometrium, so the progestogen is still needed.
- Breast
- the risk is higher with combined HRT than with oestrogen-only HRT, so a progestogen does not protect the breast.
- Million Women Study
- in this large UK study of women who had not had a hysterectomy, last use of oestrogen-only HRT was linked to a higher risk of endometrial cancer than never using HRT, whereas last use of continuous combined HRT was linked to a lower risk.
Exam traps
- A skin patch or gel does not make oestrogen alone safe for a woman with a uterus: these routes avoid the extra clot risk of tablets, but the womb lining is still unopposed.
- Drug-free breaks do not protect the womb, because a break does not oppose the growth that oestrogen causes in the lining.
- A low dose for a short time does not replace a progestogen: using HRT only for as long as needed helps to limit the breast cancer risk, but the womb lining is still unopposed.
Read the full notes
Tested in 11 SimpleMed+ questions
Practice it in Reproductive System, with the answer and a full explanation after every question.
Practice these questions