What Does Birth Control Have to Do With the Flu, Anyway?

File this one under "Huh. Who knew?" Progesterone, the sex hormone found in many forms of the birth control pill, doesn't just protect you from unplanned pregnancy -- it could also guard you from complications of the flu.

This news comes courtesy of research in the new issue of PLOS Pathogens. What? You missed it? Don't worry, we'll fill you in.

Scientists at Johns Hopkins placed progesterone implants in a group of female mice, while another group was left without. Then all the little rodents were infected with the flu. Those WITH the implants had less inflammation in their tiny lungs. They also recovered more quickly from damage to their lung cells.
We have SO many questions. Why the heck does progesterone help? And what does this have to do with us female humans who get the flu? Because let's face it -- we all worry nearly as much about getting the flu vaccine as we do about contracting the flu virus.
Let's start at the beginning.
"Lots of cells in our bodies have receptors that can bind progesterone," explains Sabra L. Klein, PhD, associate professor of molecular microbiology and immunology at Johns Hopkins Bloomberg School of Public Health and the study's lead researcher.

"Basically, progesterone can only have its effects by locking into its receptor," she adds. "Think of progesterone as a key and its receptor as a lock -- you can only activate the receptor, or open the lock, if you have progesterone, or the key."

Respiratory cells, the primary cells that get infected with flu, have these receptors. So when progesterone is present and can bind to them, it helps the lungs recover from infection.

This shows us, says Klein, "that natural hormones in our bodies or synthetic hormones that we take in contraceptives or replacement therapies affect the cells that get infected with flu." But because men and women have different levels of sex hormones (men have more testosterone, women have more estrogen and progesterone), the effects between genders will be different. 

We know what you're thinking. Get to the point! So if progesterone can help me get over the flu quicker, can I skip my flu shot if I'm on the Pill?
Not exactly.

"While both progesterone and synthetic forms of progesterone in the Pill promote faster recovery, they do not control the initial infection, replication of the virus, or damage to the lungs," Klein notes. "The vaccine or flu shot helps control the initial infection and reduces the ability of the virus to replicate and damage our lungs."

In other words, "the results of this mouse study should not be interpreted to mean that women should not get the flu shot," Klein says. "Get your vaccine. It's safe and effective."

But don't worry. You haven't heard the last about the potential superpowers of progesterone. Although it's a sex hormone that's most often studied in the context of reproduction, "I think that this study reminds us that women's health extends beyond the reproductive tract," says Klein.

Image via iStock.com/stickasa
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