How is progesterone used to regulate abnormal bleeding?
There are two ways that progesterone can be effective to regulate abnormal menses or bleeding. If given continuously such as in birth control pills or with postmenopausal hormone replacement therapy, progesterone will prevent menstrual sloughing as long as there is a small amount of estrogen present.
If birth control pills are taken continuously so that a woman skips the week of the "placebo" or inactive pills and immediately begins a new pill pack, then she will not have any menses at all.
This is the pill regimen used for endometriosis to suppress endometrial growth and thus inactivate endometriosis. If progesterone doses are too small without any estrogen around, such as with the "mini" birth control pill, breakthrough bleeding often occurs because estrogen is needed to stabilize the blood vessels in the base layer of the endometrium. Such bleeding would be called atrophic bleeding since the tissue is very bare down to its basal layer.
The second way in which progesterone is used to control abnormal menstrual bleeding is to induce a menses by giving a bolus of progesterone and then discontinuing it. This could be by a shot of progesterone in oil or by taking 5-10 days of progesterone or progestogen by pill.
The rule-of-thumb has been that if a woman is not pregnant and estrogen had previously stimulated even a small amount of endometrial growth, then a menstrual-like bleed would result within about 10 days of stopping the progesterone.
Unfortunately, this regimen only works 70-95% of the time with the shots being less effective and the progestogens (Provera®, dydrogesterone) being 90-95% successful.
Common doses used to induce withdrawal bleeding would be:
- medroxyprogesterone acetate (Provera®) 5 mg twice a day or 10 mg once a day for 5 days
- micronized progesterone 200 - 300 mg for 10 days
- progesterone in oil shots intramuscularly, 100-200 mg for one dose
- oral contraceptive pills (most monophasic pills with all the same dose of estrogen and progestogen), one pill each day for 4-5 days (for example using pills out of a pill pack or using the emergency contraceptive regimen but taking one pill each day for 4 days instead of all at once.
Sometimes if the bleeding has been quite heavy or prolonged, the progestogens will be given longer than 5-10 days just to allow a woman's recovery from the constant bleeding and blood loss.