FST and rheumatoid arthritis: Bone turnover and the markers for muscle, i.e. myostatin (MSTN), follistatin (FSTN), growth differentiation factor (GDF-15) and for bone, i.e. sclerostin (SOST), dickkopf 1 (Dkk1), periostin (PSTN) metabolism were determined in 24 female RA patients and matched healthy controls.