Hormone concentrations in synovial fluid of patients with rheumatoid arthritis

Alterations in local concentrations of hormones, affecting directly synovial cells, could be involved in the modulation of the rheumatic inflammatory processes. The aim of present study was to investigate the levels of selected hormones (steroids, peptide and thyroid hormones) in synovial fluid of knee joint of patients with rheumatoid arthritis (RA) and control individuals with non-rheumatic exudate (with osteoarthrosis, OA).

Thirty-eight patients, 22 female and 16 males, with rheumatoid arthritis (RA) and 12 subjects with osteoarthrosis (OA, control group, 6 females and 6 males) participated in the study. Concentrations of cortisol (CS), 17-beta-estradiol (ES), dehydroepiandrosterone (DHEA), progesterone (PRG), aldosterone ALD), prolactin (PRL), insulin (INS), and C-peptide were determined by radioimmunoassay in synovial fluid. Insulin binding to isolated cell membrane of cells from synovial sediment was estimated by using radioiodine labeled insulin. In a group of patients (10 with RA and 4 with OS), the levels of free threeiodothyronine (FT3), TSH and growth hormone (GH) were also determined in synovial fluid.

Increased levels of ES in synovial fluid of RA patients were observed, and higher differences were noted in men. TE concentrations were moderately elevated in synovial fluid of RA patients, however the ratio of ES/TE was significantly higher in male RA compared to OA patients. Higher levels of PRG, ALD and growth hormone were noted in synovial fluid of RA patients. Besides the steroid hormones the presence of insulin and C-peptide was noted in synovial fluid and the correlation between the levels of these two peptides was highly significant. The concentrations of INS and C-peptide in synovial fluid of patients from RA and OA group were not significantly different, however, highly significant increase of insulin binding to isolated membrane of synovial cells was found. Concentrations of cortisol, dehydroepiandosterone, prolactin, TSH and FT3 in synovial fluid were not significantly different in RA and OA groups.

Besides the steroids also insulin, c-peptide, GH and FT3 were found in synovial fluid. The elevated ALD and GH levels in synovial fluid of RA patients and the presence of INS in synovial fluid with increase of INS binding to plasma membranes of cells from synovial fluid of RA patients suggest that besides the gonadal steroids also these hormones may affect the local inflammatory processes.