Progesterone May Ease Influenza

Researchers from the Johns Hopkins Bloomberg School of Public Health have discovered that sex hormones have an effect that extends far beyond the reproductive system; progesterone may eventually be a possible flu treatment for women. Progesterone, a female hormone contained in the majority of hormone-based birth control, appears to fend off the worst effects of influenza. As an unexpected bonus, it seems to assist damaged lung cells in healing more rapidly.

According to the World Health Organization (WHO), over 100 million women of reproductive age are using progesterone-based contraception. Women in this age range are twice as likely to suffer from complications related to influenza. "Despite the staggering number of women who take this kind of birth control, very few studies are out there that evaluate the impact of contraceptives on how the body responds to infections beyond sexually-transmitted diseases," says Sabra L. Klein, PhD, an associate professor in the Bloomberg School's Department of Molecular Microbiology and Immunology, and leader of the study. "Understanding the role that progesterone appears to play in repairing lung cells could really be important for women's health. When women go on birth control, they don't generally think about the health implications beyond stopping ovulation and it's important to consider them."

Klein and her colleagues inserted progesterone implants into a group of female mice, leaving the second group of female mice without. The mice in both groups were then infected with the influenza A virus, resulting in both sets of mice becoming ill. The mice with the implants had better lung function and less pulmonary inflammation. Additionally, the damage to their lung cells repaired more rapidly.

Progesterone was discovered to be protective against the more serious effects of the flu when the researchers increased the production of a protein called amphiregulin by the cells lining the lungs. When they bred mice that were depleted of amphiregulin, the protective effects of progesterone depreciated as well. Klein says that she was not surprised at the lessening of inflammation and damage associated with the flu, but she was surprised at the assistance in inducing lung cell repair.

Levels of progesterone fall when female mice, and most likely humans, become ill with the flu. Women taking birth control pills, IUD’s, or injections receive a steadier level of progesterone, overriding what the ovaries produce naturally, or what the virus eliminates during infection. According to Klein, there is currently no scientific data proving that there is a link between progesterone in humans and flu severity, because this has never been explored by researchers previously. Researchers at the Johns Hopkins Center of Excellence for Influenza Research and Surveillance will be furthering this research and have added specific questions about birth control to their questionnaires in order to get a clearer idea of how this protective effect may work with the human population. Klein and her colleagues are now attempting to determine the exact mechanism by which progesterone increases the level of amphiregulin in the lungs. The mice in the original study were given actual progesterone and not a synthetic form of the hormone, which is what is used in contraception. More recently, as part of their ongoing research, Klein and her colleagues gave synthetic progesterone to mice with similar results. Their hope is to be able to ultimately figure out a way that this could work in humans, to keep women from experiencing complications from the flu.