Pill may be protecting women from flu effects, says study
A hormone commonly found in contraceptive pills may protect women from the worst effects of flu and help repair lungs damaged by the illness, a new study reveals.
Trials of progesterone, which is present in most forms of hormone-based birth control, appeared to stave off the worst effects of influenza in female mice.
The unexpected finding by scientists at Johns Hopkins University in Baltimore, Maryland, indicates that the sex hormone may have an effect far beyond the reproductive system and may one day offer a viable flu treatment.
Women of reproductive age are twice as likely as men to suffer from complications related to the flu virus.
The researchers are now calling for further investigations to establish whether women taking progesterone-based contraception, of whom there are an estimated 100 million worldwide, are enjoying unexpected protection from flu while on the pill.
Dr Sabra Klein, who led the study, which is published in the journal 'PLOS Pathogens', said: "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.
"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," she added.
The research team infected a cohort of mice with an influenza A virus, some of which had been implanted with progesterone and some not.
Both sets of mice became ill, but those which had the implants suffered less pulmonary inflammation, better lung function and saw the damage to their lung cells repaired more quickly.
The study found that progesterone was protective against the more serious effects of the flu by increasing the production of a protein called amphiregulin by the cells lining the lungs.
When the researchers bred mice that were depleted of amphiregulin, the protective effects of progesterone disappeared as well.
Dr Klein said she was not surprised progesterone lessened the inflammation and damage associated with the flu, but that she had not expected the hormone to help repair lung cells as well.
When female mice, and probably humans, get sick with flu their natural levels of progesterone fall.
But women on hormonal contraceptives get a steadier level of progesterone which overrides what the ovaries make naturally or what the virus takes away during infection.