Low testosterone levels may be an early warning sign of rheumatoid arthritis in men, a new study has warned.
According to the study, published in the journal Annals of the Rheumatic Diseases, scientists studied participants of the Swedish Malmo Preventive Medicine Program (MPMP), which began in 1974 and tracked the health of more than 33,000 people born between 1921 and 1949.
Participants were subjected to a battery of tests, completed a questionnaire on health and lifestyle factors, and left blood samples after an overnight fast.
The authors identified all those MPMP participants who were subsequently diagnosed with rheumatoid arthritis up to December 2004.
Stored blood samples were available for 104 of the men who subsequently developed rheumatoid arthritis, and for 174 men of the same age who did not develop the disease.
Rheumatoid factor status was known at diagnosis for 83 of the men, almost three out of four (73 per cent) of whom tested positive for it; the rest tested negative.
Rheumatoid factor is an antibody that indicates disease severity and is used to categorise the condition.
After taking account of smoking and body mass index, both of which can affect the risk of rheumatoid arthritis, men with lower levels of testosterone in their blood samples were more likely to develop the disease, the study found.
This was statistically significant for those who tested negative for rheumatoid factor when they were diagnosed.
These men also had significantly higher levels of follicle stimulating hormone - a chemical that is involved in sexual maturity and reproduction - before they were diagnosed with rheumatoid arthritis.
This is likely to be secondary to reduced testosterone production, said the authors in a British Medical Journal statement.
The findings prompted them to suggest that hormonal changes precede the onset of rheumatoid arthritis and could influence disease severity.
