Led by Mary Fran R. Sowers of the University of Michigan in Ann Arbor, MI, the study included 842 premenopausal or perimenopausal women from the Southeast Michigan Arthritis Cohort. The women had annual X-rays of both knees along with analysis of blood levels of estradiol and urine levels of 2-hydroxyestrone and 16-hydroxyestrone, two oestrogen metabolites. Patients were also interviewed regarding pain, health, and lifestyle and were followed for three years.

The results showed that the women who developed knee OA during the study period had greater odds of having estradiol concentrations and urinary 2-hydroxyestrone levels in the lowest third of the study population, and a higher ratio of 2-hydroxyestrone to 16-hydroxyestrone, even after adjusting for other risk factors.

"Selected work with animal models provides support for the increased odds of developing OA with lower estradiol concentrations," the authors note. This is one of the few studies that has actually examined hormone concentrations, particularly in relation to new cases of OA, and the first to examine levels of oestrogen metabolites. The authors hypothesise that the role of higher 2-hydroxyestrone concentrations in delaying the development of knee OA may be partially through the metabolism of arachidonic acid, a compound from which cells involved in inflammation (such as leukotrienes) are produced, since oestrogen metabolites have been shown to play an important role in this pathway.

Previous studies have shown that altered patterns of oestrogen metabolism are present in rheumatoid arthritis and systemic lupus erythematosus, suggesting an association with symptoms, such as pain and inflammation, as opposed to disease onset and progression due to structural changes.

MEDICA.de; Source: John Wiley & Sons, Inc.