Increased estrogen formation and estrogen to androgen ratio in the synovial fluid of patients with rheumatoid arthritis.

Objective: It has been proposed that physiologic levels of estrogens stimulate immune responses whereas androgens suppress inflammatory reactions. Thus, prevalence of synovial androgens relative to estrogens would be favorable in rheumatoid arthritis (RA). We investigated synovial fluid (SF) concentrations of several estrogens and androgens and conversion products of the sex steroid precursor dehydroepiandrosterone (DHEA) in supernatants of mixed synoviocytes.

Methods: SF steroid concentrations were measured by high performance liquid chromotography and mass spectrometry in 12 patients with RA and 8 subjects with traumatic knee injury (noninflammatory controls). Conversion of DHEA to downstream hormones was measured by thin-layer chromatography and phosphorimaging detection in 3 patients with RA and 3 patients with osteoarthritis (OA).

Results: Overall, SF concentration of free estrogens tended to be higher in RA patients versus controls (p < 0.06). Molar ratio of free SF estrogens/free SF androgens was elevated in RA compared to controls (1.17 +/- 0.32 vs 0.29 +/- 0.08, without unit; p = 0.017). The free SF concentration of the precursor androstenedione was significantly higher in RA patients than in controls (104.6 +/- 32.6 vs 30.4 +/- 0.4 ng/ml; p = 0.011), and SF estrone the aromatase conversion product of androstenedione was also elevated in RA compared to controls (13.6 +/- 2.6 vs 6.6 +/- 0.8 ng/ml; p = 0.035). The biologically active estrogen derivatives, 16a-hydroxyestrone and 4-hydroxyestradiol, were both higher in RA compared to controls (p = 0.085 and p = 0.044, respectively). In mixed RA synoviocytes, DHEA conversion yielded high local levels of 17beta-estradiol (708 pmol/l = 0.193 ng/ml) compared to testosterone (88 pmol/l = 0.026 ng/ml).

Conclusion: SF levels of estrogens relative to androgens are significantly elevated, while those of androgens are markedly reduced, in patients with RA compared to controls. This imbalance is most probably due to increased aromatase activity. Thus, an available steroid precursor, such as DHEA, may be rapidly converted to proinflammatory estrogens in the synovial tissue, which may in turn stimulate the inflammatory process in patients with RA.