APOA1 and synovial sarcoma: In addition, the serum levels of hematocrit (HCT), hemoglobin (HGB), and apolipoprotein A1 (APOA1) in preadolescents with SS were significantly lower than those in the control group, while free thyroxine (FT4) was higher in preadolescent GHD (PAG) and preadolescent ISS (PAI) than in the controls.