Serum iron and serum hepcidin levels are directly and indirectly associated with osteoporosis in patients with rheumatoid arthritis (RA), according to study results published in Scientific Reports.1
Previous research has reported lower serum hepcidin and higher serum iron levels in patients with osteoporosis.2 In this study, investigators aimed to determine the correlation between serum hepcidin levels and degree of osteoporosis in patients with RA.
A total of 262 patients with RA were included in the study (77.5% women; mean age, 67.5±11.4 years), a majority of whom had low disease activity (82.4%) or were in remission (77.1%), according to disease activity score in 28 joints based on C-reactive protein (DAS28-CRP) and Clinical Disease Activity Index. Data on disease characteristics indicated a mean disease duration of 13.6±10.6 years, with mean disease activity scores of DAS28-CRP and erythrocyte sedimentation rate of 2.2±1.5 and 2.6±1.0, respectively. Measurements of mean serum hepcidin (14.3±19.7 ng/mL), fibroblast growth factor (FGF23; 59.3±32.9 pg/mL), and 25(OH)D levels (16.5±6.9 ng/mL) were also collected. Study participants were categorized into 4 groups based on these levels and associations with disease parameters were analyzed.
Higher hepcidin levels were related to increased inflammation, higher ferritin and iron levels, lower unsaturated iron binding capacity, and higher 25(OH)D levels. In addition, RA inflammation and 25(OH)D levels were significantly related to serum hepcidin levels. Higher serum 25(OH)D levels were associated with older age, lower estimated glomerular filtration rate (eGFR), higher ferritin and hepcidin levels, and higher Z score of femoral activity. Higher serum FGF23 levels were associated with older age, lower eGFR, higher body mass index, and 25(OH)D levels.
Overall, results indicated that serum iron levels were positively correlated to bone mineral density (BMD), and serum hepcidin and ferritin levels were positively related to 25(OH)D levels, which were positively associated with the femoral Z score. Serum hepcidin levels and iron metabolism were shown to both directly and indirectly affect osteoporosis in patients with RA.
Study limitations included the use of data from a single center and the absence of control participants. In addition, lifestyle factors such as diet, smoking, and alcohol intake were not analyzed.
1. Sato H, Takai C, Kazama JJ, et al. Serum hepcidin level, iron metabolism and osteoporosis in patients with rheumatoid arthritis [published online June 18, 2020]. Sci Rep. doi:10.1038/s41598-020-66945-3
2. Liu B, Liu C, Zhong W, Song M, Du S, Su J. Reduced hepcidin level features osteoporosis. Exp Ther Med. 2018;16:1963-1967.