beta-Endorphin, immunological and biochemical changes in synovial fluid in rheumatic disorders.

In 120 patients with rheumatic disorders concomitant assays of serum and synovial fluid were done for acute phase reactants, immunoglobulins and the neuropeptide beta-endorphin. One-third of the patients with rheumatoid disease demonstrated synovial fluid levels of endorphin to be several-fold higher than serum levels, while in two-thirds the opposite results were found. These changes are discussed as adaptive or defense mechanisms. The synovial membrane is postulated to synthesize beta-endorphin.