Synthetic hormones, such as those found in contraceptive pills, injections, and patches, may affect brain development during adolescence, according to new research. The study, performed in rats, showed an association between hormonal birth control and higher levels of a stress hormone, as well as signaling changes in the prefrontal cortex.
The researchers stress that these findings should not be a cause for alarm for adolescents who are currently taking these medications or their caregivers.
“Birth control has had a major positive impact for women’s health and autonomy – so it’s not that we’re suggesting adolescents should not take hormonal contraceptives,” said senior author Benedetta Leuner in a statement.
“What we need is to be informed about what synthetic hormones are doing in the brain so we can make informed decisions – and if there are any risks, then that’s something that needs to be monitored.”
Previous research has suggested that there could be a link between hormonal birth control and depression. In the new study, the team from Ohio State University specifically looked at the potential effects of contraceptives while the brain is developing in adolescence.
According to statistics from The American College of Obstetricians and Gynecologists, almost 5 percent of girls and women aged 15-19 years in the US use a long-acting reversible contraceptive (LARC) method. Most LARC methods, such as injections and implants, contain synthetic hormones.
While there are efforts to develop long-term male contraceptives (some more out-there than others), the lack of options means that the burden of contraceptive planning still rests primarily on women's shoulders.
However, it's also important to note that these products can be prescribed for lots of other reasons, not only for birth control. For example, hormonal contraceptives are a common treatment for heavy periods.
Despite their widespread use, there's still a lot that scientists don’t know about how synthetic hormones may affect the brains of teenagers. “Adolescence is a crucially under-investigated period of dramatic brain change and dramatic hormonal change that we really haven’t understood,” said study author Kathryn Lenz.
In the study, a combination of estrogen and progesterone – hormones commonly used in birth control – was given to adolescent female rats for a period of three weeks. The researchers then took blood samples, and were able to show that the rats had elevated levels of another hormone, corticosterone, compared with untreated animals. This is similar to the human hormone cortisol, known to be associated with stress.
When the rats were exposed to environmental stress and given time to recover, their corticosterone levels remained high. Their adrenal glands were also enlarged; adrenaline, or epinephrine, is another key hormone involved in stress.
The team wanted to get to grips with what was happening in the animals’ brains, so they analyzed the patterns of gene activation in the prefrontal cortex. This region of the brain undergoes continuous development throughout adolescence.
The results showed decreased excitatory synapses, but no change in inhibitory synapses. This imbalance could affect the normal signaling patterns in this region and lead to behavioral changes.
“What this means for the function of particular circuits, we don’t know yet. But this gives us a clue of where to look next in terms of what the functional outcomes might be,” said Lenz.
Although these results are limited to rats for now, they do raise interesting questions for the researchers to explore when it comes to the use of contraceptives in adolescent humans.
“These are synthetic hormones, so are they affecting the brain because of their synthetic properties, or are they affecting the brain because they’re blocking the naturally produced hormones?” Leuner commented. “It’s a difficult question to answer, but an important one.”
The study was presented as a poster at the 2022 annual meeting of the Society for Neuroscience.