In my late teens and early 20s, I had some bad experiences with birth control side effects: insomnia, panic attacks, heavy bleeding, etc. I actually went on and off the pill several times before I realized that my symptoms and the pill were connected. I have not used hormonal birth control since then and have never had these issues again. As I turn 40 this year, I am concerned about approaching perimenopause and how HRT might affect me. Is there any data about previous experiences with the birth control pill and taking hormones during perimenopause?
—Harrowed about Hormones
Many women struggle with side effects like those you describe while taking birth control pills (BCPs). I am sympathetic to your concern — I had to stop taking birth control pills in my 20s because they were increasing my blood pressure. Women worry about this because BCPs and hormone replacement therapy (HRT) have common ingredients: both typically contain estrogen and progesterone. However, I have not found any data on how likely those side effects are to recur with HRT.
In the absence of data, how can we consider the risks and benefits of hormone replacement therapy when we have had side effects or adverse events with birth control pills?
Most BCPs are a combination of one type of estrogen — ethinyl estradiol — and a synthetic progestin. What makes one pill different from others is the dose of ethinyl estradiol and the type and dose of progestin. HRT for most women will include estrogen as estradiol or conjugated equine estrogens, and progesterone or a synthetic progestin.
But there are several differences between BCPs and HRT. The biggest difference is dose. The dose of estradiol in even the lowest-dose BCPs is three to four times the dose of estrogen in HRT. The lower dose of estrogen in HRT may result in fewer side effects.
Additionally, while there are birth control patches, most women have taken birth control pills. Women often take estradiol for HRT through the skin as a patch or gel. Estradiol is metabolized differently if you take it by mouth versus through the skin. This may result in differences in side effects for some women.
The options for taking progesterone for HRT are also broader. You can take a pill, get it through the skin, or get it from a progestin-eluting IUD. You can take progesterone or you can take synthetic progestin. Different synthetic progestins have different effects in the body that are well understood. Knowing which BCP you took in the past and what side effects you experienced will help your doctor choose which form of progesterone might work well for you.
All of this is to say, while there is little data on whether women will experience the same side effects with BCPs and HRT, there is reason to think we might not. If you are having perimenopausal symptoms, it would certainly be reasonable to try HRT and monitor for side effects. You might be pleasantly surprised.
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