For women in whom the uterus (womb) is present, a progestogen is added to the estrogen to reduce the risk of estrogen causing thickening, and possibly cancer of the endometrium (lining of the womb). Progestogens are mostly made from plant sources and resemble the naturally occurring progesterone, usually produced from the ovary in the second half of the menstrual cycle. The two main types of progestogen currently used in HRT are: those most closely resembling progesterone (dydrogesterone, drospirenone medroxyprogesterone acetate and micronised progesterone) and those derived from testosterone (norethisterone, norgestrel and levonorgestrel).
If side effects are experienced on one type, changing the type or route of progestogen may help.
The duration and frequency of the progestogen determines the presence and pattern of bleeding and the type used is influenced by presence or absence of periods and age.
HRT in the Perimenopause: If HRT is commenced in the early stages of ovarian decline when periods are still present (the perimenopause), estrogen is taken every day and progestogen for 10 to 14 days per month (sequential HRT). This cyclical progestogen induces a monthly withdrawal bleed in about 85% of women. If the periods are becoming infrequent, the progestogen can be taken for 2 weeks every 3 months, inducing a 3 monthly bleed (long cycle HRT).
HRT in the Postmenopause: If the periods have been stopped for more than 1 year (postmenopause) before starting HRT, or the women is aged 54 or more, progestogen can be taken every day along with the estrogen (continuous combined HRT). Continuous combined, or period-free HRT, may cause some bleeding in the first 6 months, but should not induce bleeding thereafter.
- Mirena Coil.
This is a small device which fits inside the womb like an intrauterine conceptive device. It can usually be fitted in an out-patient clinic with minimal discomfort. Not only is it a contraceptive, but also it releases a small amount of progestogen hormone to the womb lining, making it thinner and hence making heavy periods lighter. At first it can sometimes be associated with irregular spot bleeding, which can be irritating, but this nearly always settles. Mirena can be used to provide the progestogen part of HRT in both the perimenopause and the postmenopause. With a Mirena in place, any form of estrogen can be used to control menopausal symptoms. Mirena is particularly helpful when there are heavy bleeds with sequential HRT, when contraception is still required along with HRT, and when there are side effects from the progestogen part of HRT.