Why Birth Control Might Not Work for Endometriosis

Years after I stopped taking hormonal birth control — pills and then the NuvaRing — I looked for answers as to why it never eased my symptoms (and made them worse). It turns out, research supports the idea that birth control may be ineffective at symptom relief because endometrial tissue can be progesterone resistant, a condition that affects people with endometriosis, polycystic ovarian syndrome, and fibroids, and plays a part in endometrial and breast cancers.1,2

I always knew progesterone was a bit of a drag for me; I start to feel crappy 12 days before my period starts, right as my uterine lining — and my endo belly — begins to thicken. But I'll admit I was a little confused by the term. How can I be progesterone resistant if I produce progesterone? So last year I asked Kaylon Bruner-Tran, a professor of obstetrics and gynecology at Vanderbilt University who researches endometriosis, to help me understand.

What is progesterone resistance (PR)?

Bruner-Tran told me it might be more accurate to call it “reduced endometrial progesterone responsiveness". That means women with endometriosis, in general, don't respond as well to the hormone as people without endo.

"In our studies, about 30% of endometriosis patients had normal or near normal response to progesterone, while 70% had some degree of diminished response", said Bruner-Tran.

This a problem because progesterone is supposed to decrease inflammation in the endometrium, but it can't if endometrial tissue doesn't respond to it.3 Plus, estrogen and progesterone should balance each other out. And they need to be in the right ratio, Bruner-Tran explained. So if I add hormones from birth control, and my endometrial tissue doesn't respond to progesterone, she said this could create an imbalance that could lead to more cramping.

The amount of progesterone resistance isn't the same for everyone and can dramatically influence how the disease manifests, she told me. A significant loss of progesterone action can lead to infertility and abnormal cycles since this hormone is vital in maintaining a pregnancy.

What causes PR?

The short answer: no one knows. Scientific hypotheses point to genetics, environmental toxins, retrograde menstruation, and a cycle of chronic inflammation. Female fetuses even have endometriosis, so some researchers think progesterone resistance develops in utero.

How does PR affect treatment?

Like anything that has to do with endometriosis, there aren't a lot of choices. But doctors and researchers are looking into it. Here are a couple of progestin-only options:

  • Dienogest, an oral progestin. Studies show it "improves progesterone resistance in endometrial tissue" and "inhibits ovulation and down regulates pro-inflammatory cytokines".4
  • Levonorgestrel intrauterine system (LNG-IUS), also known as the Mirena IUD. According to a question I posed on Facebook, many of my female friends who have complicated or painful menstrual cycles — including those with PCOS, endometriosis, and fibroids —  experienced relief with this hormonal IUD after typical birth control pills failed to help. Research also shows it helps with symptom relief for endometriosis, and reduces heavy periods and endometrial polyps.5-7

My OBGYN told me the LNG-IUS is the type of treatment she prescribes most often to her endometriosis patients. She also said it results in much less breakthrough bleeding than progestin-only pills. Though, that bleeding may take a few months (or a year, according to some of my friends who quit using the IUD) to subside.

Some women do report cramping when they first start with a hormonal IUD, which makes sense if you continue to experience bleeding. But one study showed that discontinuation was highest in the first 3-6 months and that more than half of women — those who stayed on it for 3 years — did see symptom improvement.5 Although some people I know love their IUD, it wasn’t right for everyone. Definitely talk to you doctor if your pain gets worse.

Talk to your doctor

Everyone responds to treatment differently, but know that you're not alone if combined birth control doesn't do anything to help your symptoms. While there isn't a test you can get to determine if you're progesterone resistant, bring it up with your doctor if you have questions. And if they don't know what you're talking about, bring the research with you.1

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