Hormonal drug — used in some birth controls — linked to brain tumors, study says
The long-term use of a synthetic hormone commonly used in gynecology has been linked to an increased risk of brain tumors, according to a new study.
More than 18,000 women were included in the study in France to examine the risk factors of prolonged use of progestogens. The findings were published in the British Medical Journal on March 27.
The researchers followed women using different types of synthetic forms of the hormone progesterone, commonly used to treat a variety of gynecological conditions such as endometriosis, PCOS, menopausal hormone therapy and in some contraceptives.
The study saw a significant increase in a specific type of brain tumor, a meningioma, when women used the drugs for a year or more, often requiring surgery, according to a March 27 news release.
Here is what you need to know.
What are synthetic hormones?
Progestogens include synthetic variations of the natural hormone progesterone, the researchers said.
Progesterone is a sex hormone that regulates the menstrual cycle, pregnancy and other functions of the reproductive system, and it is created in ovaries, according to the Cleveland Clinic.
Synthetic hormones are drugs that mimic the actions of natural hormones, acting as either an additional source of the hormone, or as a replacement.
That means when there is a condition impacting the female reproductive system, physicians can prescribe synthetic hormones to get the system back on track or treat the symptoms.
One variation, medroxyprogesterone acetate, is also the main synthetic hormone used in injectable contraception, according to the study.
Birth control shots are currently used by 74 million people worldwide, the researchers said, including 2 million American women who filled a prescription in 2020. In total, 1 in 5 American women have reported using the shot as birth control at some point in their lives.
Multi-fold increase in risk
The French researchers used data from their national health system to look at the medical history of more than 18,000 women who were treated for the meningioma brain tumors between 2009 and 2018, according to the study.
“Meningiomas are mostly non-cancerous tumors in the layers of tissue (meninges) that cover the brain and spinal cord,” the researchers said in the release. “Factors such as older age, female sex, and exposure to three high-dose progestogens (nomegestrol, chlormadinone, and cyproterone acetate) are already known to increase the risk of meningioma.”
If a woman came to the hospital for surgery on her brain tumor, the researchers looked at her previous history of progestogen use, and noted what type of synthetic hormone she was taking and for how long, according to the study.
They found that women who use medrogestone for a year or more had a 4.1-fold increased risk of developing the brain tumor, and those who had prolonged use of promegestone had a 2.7-fold increased risk.
Women with tumors who had used the birth control injection had a 5.6-fold increased risk of developing a meningioma when taking the shot over multiple years, the researchers said in the release.
The researchers said it is important to note that the results come from an observational study, meaning no direct cause and effect relationship can be established, only that the risk of the tumor increases when the drugs are also used.
The study also notes the birth control shot, while not commonly used in France, is used in many other countries, particularly for women in vulnerable populations.
This includes people suffering from mental illness, who may not be able to maintain a schedule of a daily dose like the birth control pill.
Building on previous research
The study joins numerous others linking hormonal drugs to increased cancer risk.
A previous French study, published in 2021, examining the synthetic female hormone cyproterone acetate found a seven-fold increase in risk of brain tumors when it was used at a high dose from 5 to 30 years.
A 2023 study out of Denmark found hormone therapy containing estrogen increased the risk of tumors on the central nervous system, particularly from drugs used to help treat symptoms of menopause.
Oral contraceptives, which use the synthetic versions of hormones estrogen and progesterone, have been linked to increased risk of breast cancer and cervical cancer, according to data from the National Cancer Institute.
Because of the widespread use of synthetic hormonal drugs around the world, the researchers said more research is needed to study the side effects of long-term use.
This story was originally published March 28, 2024 at 1:56 PM with the headline "Hormonal drug — used in some birth controls — linked to brain tumors, study says."
