Men with low levels of the hormone, testosterone, may be more likely to go on to develop rheumatoid arthritis (RA), a new study indicates.

RA is a chronic and often painful disease affecting the joints, causing them to become inflamed. An inflamed joint looks swollen and red and appears warm to touch. This inflammation can lead to permanent damage in the joints if the disease is not treated. Around 40,000 people in Ireland are affected.

According to Swedish scientists, sex hormones are thought to have a role in the development of RA. However, while both men and women with the condition tend to have lower levels of testosterone compared to people without it, until now, it has been unclear whether the hormone played a role in the development of RA or was a consequence of it.

The scientists decided to investigate this further. They looked at over 33,000 people who had been taking part in a long-term study aimed at tracking their health. This included the participants completing detailed questionnaires and providing blood samples.

The study found that men with lower levels of testosterone in their blood samples were more likely to go on to develop RA. The results stood even when two other factors that can affect the risk of RA were taken into account - body mass index (BMI) and smoking.

The men were also found to have higher levels of follicle stimulating hormone, which is important for sexual maturation and reproduction, before they were diagnosed with RA. However, the scientists believe that this ‘is likely to be secondary to reduced testosterone production'.

They believe that the study shows that hormonal changes precede the onset of RA and may even influence the severity of the disease.

Details of this study are published in the journal, Annals of the Rheumatic Diseases.

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