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Why do females fare worse than males with cystic fibrosis?

A new study from the Royal College of Surgeons in Ireland shows that the female hormone oestrogen has a role to play in this.

Cystic Fibrosis patient Sara Cahoon
Cystic Fibrosis patient Sara Cahoon
Image: Chris Butler/AP/Press Association Images

A MAJOR BREAKTHROUGH has been made in discovering why females with cystic fibrosis do worse than males, thanks to the Royal College of Surgeons in Ireland.

A study undertaken by researchers from the Respiratory Research Division of the Department of Medicine at the RCSI is the first to show that the female hormone oestrogen promotes the presence of a particular form of bacteria which results in more severe symptoms for female CF patients.

Female hormones

The study also showed that females who were taking the oral contraceptive pill had lower levels of the problematic bacteria, because the pill decreases the amount of naturally occurring oestrogen in their bodies.

The study is published in the New England Journal of Medicine. It showed that oestrogen promoted the presence of a ‘mucoid’ form of the bacterium Pseudomonas aeruginosa in the lungs of women with CF.

These bacteria are coated in a slimy layer which makes them more difficult to treat with antibiotics, the scientists said. They are also difficult to clear with they body’s own natural defences and this leads to significant lung inflammation.

The researchers said this helps to explain, “at least in part, why females with cystic fibrosis often have a worse outcome than males”.

New understanding

Professor Gerry McElvaney, Director of the Respiratory Research Laboratory RCSI/Beaumont Hospital, and joint senior author on the paper, commented:

This study opens the way to a new understanding and potentially new therapies in the treatment of cystic fibrosis, a condition in which Ireland has the highest incidence in the world. This research study is among the first examples which shows the effects of gender hormones on infections and therefore has major implications for conditions beyond cystic fibrosis including other respiratory diseases such as asthma.

Cystic fibrosis is a life threatening inherited disease. It primarily affects the lungs and the digestive system and a build up of mucus can make it difficult to clear bacteria. This leads to cycles of lung infections and inflammation, which can eventually lead to damage of the lungs.

Ireland has the highest incidence of CF in the world, at 2.98 per 10,000. It also has the highest carrier rate in the world, with 1 in 19 individuals classed as carriers. Right now there are approximately 1,200 people with CF living in Ireland.

Funding and authors

The cystic fibrosis research in this paper is funded by the Health Research Board, Medical Charities Research group, Science Foundation Ireland, Molecular Medicine Ireland (MMI), CF Hopesource, and Irish CF research trust. It was also funded by individual donors such as Fergal Somerville, who recently swam the English Channel in support of CF research in Beaumont Hospital.

This paper illustrates interdepartmental and inter-institutional links at RCSI, as co-authors on the paper include colleagues from the Departments of Medicine (Dr Sonya Cosgrove), General Practice (Dr Borislav Dimitrov) and Molecular Medicine (Professor Brian Harvey), RCSI; Beaumont Hospital/RCSI (Dr Cedric Gunaratnam, Professor Shane O’Neill); and the School of Medicine (Dr Stephen Smith), Trinity College, Dublin.

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