BETHESDA, Md., Jan. 15 (UPI) -- Estrogen decreases the ability of the influenza A virus to replicate in cells, offering a protective effect for women against the flu, researchers at Johns Hopkins University found in a recent study.
In addition to showing estrogen's effects on flu, the researchers observed how estrogen prevents the virus from copying itself inside cells. Less replication of a virus in cells lessens the severity of an infection, and lowers the chance people will spread the virus.
Previous research with animals has shown estrogen had protective effects against the flu, and the female sex hormone is already known to have antiviral properties against HIV, Ebola and hepatitis, researchers said.
"Because estrogen levels cycle in premenopausal women, it may be difficult to see this protective effect in the general population," said Dr. Sabra Klein, a researcher at Johns Hopkins University, in a press release. "But, premenopausal women on certain kinds of birth control or post-menopausal women on hormone replacement may be better protected during seasonal influenza epidemics."
For the study, published in the American Journal of Physiology: Lung Cellular and Molecular Physiology, the researchers exposed nasal cells from men and women to estrogen, the environmental estrogen bisphenol A and selective estrogen receptor modulators, or SERM.
All three forms of the hormone reduced replication in women's cells, but not in men's. In women, estrogen stopped the virus from making copies of itself using estrogen receptor beta, a new finding Klein said would help future research on estrogen's antiviral effects.
"We see clinical potential in the finding that therapeutic estrogens that are used for treating infertility and menopause may also protect against the flu," Klein said.