PROGESTERONE appears to lessen the symptoms of influenza infection and facilitate the speedier recovery of the lungs, according to results of a recent study. The researchers revealed prior to the study that the results were unexpected; the lead investigator, Prof Sabra L. Klein, Molecular Microbiology and Immunology, and Biochemistry and Molecular Biology, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, USA, revealed: “We initially thought that progesterone may make flu worse in females because pregnancy is a known risk factor. Instead, we observed that progesterone significantly protected female mice against severe disease by mitigating inflammation and improving pulmonary function.”
The research team implanted one group of female mice with progesterone, leaving another group without. Both groups were then infected with the influenza A virus. While both groups became unwell, the mice with progesterone implants presented reduced pulmonary inflammation, better lung function, and any lung damage was repaired at an increased rate. Commenting on this surprise finding, Klein commented: “[The] observation got us thinking about how the lungs repair themselves after an infection, which brought us to growth factors, like amphiregulin. When we measured amphiregulin, sure enough, it was unregulated in females treated with progesterone.” To test this theory, the team infected mice that did not produce amphiregulin with influenza. As they predicted, these mice did not benefit from progesterone’s protective effect.
Typically, when females are infected by influenza, their progesterone levels will naturally fall. However, any females taking progesterone-based medication receive a constant stream of progesterone, preventing their levels from falling. With a progesterone analogue being the primary constituent of the female contraceptive pill, taken by an estimated 100 million young adult women globally, this is a potentially far-reaching finding. There is great scope for further research to investigate how the protective effect of progesterone and its synthetic forms might work in humans. Klein’s team has already begun this process, with Klein explaining that: “We are now conducting studies showing that synthetic forms of progesterone, including levonorgestrel, found in hormone contraceptives and hormone replacement therapies also protect against flu, which has farther reaching implications.”
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