MON-LB073 The Serum Creatinine to Serum Cystatin C Ratio Is a Reliable Surrogate Marker of Sarcopenia in Patients with Cushing's Syndrome in Remission

Sarcopenia, the loss of skeletal muscle mass and function, is a frequent finding in patients chronically exposed to glucocorticoids. Patients with active Cushing’s syndrome (CS) show reduced muscle mass and weakness. Decreased MRI-measured lean mass has been found in CS after 20 months since successful therapy vs. pre-treatment. Persistence and worsening of muscle strength has been described in CS despite long-term remission, suggesting that previous exposure to excessive cortisol may have induced irreversible alterations of muscle structure and function. Low muscle mass can be detected using several techniques, including dual-energy X-ray absorptiometry (DXA), ultrasonography (US), magnetic resonance imaging (MRI) and computed tomography (CT), while low muscle strength and performance can be diagnosed through functional testing. The Sarcopenia Index (SI),-(serum creatinine value [mg/dl]/serum cystatin C value[mg/L]) × 100, has been proposed as a potential, reliable surrogate marker of low muscle mass and function. Clinical usefulness of this parameter in CS is currently unknown. The aim of our study was to establish the correlation between SI and the techniques commonly used to evaluate muscle mass, including DXA, US, MRI, as well as tests of muscle function including gait speed velocity (GS), timed up and go (TUG), 30-second chair stand and hand grip strength (HGS). We studied 30 CS women [mean(±SD) age, 50±12 years; mean(±SD) BMI, 26.7±3.8] and 30 age- and BMI-matched healthy women. We studied whole-body composition by DXA, and calculated the Skeletal Muscle Index (SMI), defined as the ratio of the DXA-measured appendicular skeletal muscle mass (ASM) [Kg] and the height squared [m(2)]. We evaluated US muscle thickness using transverse images of rectus femoris and vastus intermedious at the midpoint and at the distal third. We measured the volume of lean mass (DxLean; ml) of the thigh muscles using MRI, 3-point Dixon sequences. SI was associated with both US-measured section of the distal third of the right rectus femoris (ρ=0.47, p=0.008), and the DxLean (ρ=-0.46, p=0.011) in patients. We found no correlations between SI and either SMI or DXA-measured lean mass (gr) (p=n.s.). SI was negatively associated with both total body fat mass (gr) (ρ=-0.45, p=0.010) and trunk fat mass (gr) (ρ=0.065 p<0.001). SI was related to GS (ρ=0.416, p=0.022), TUG (ρ=-0.544, p=0.002), 30-sec chair stand (ρ=-0.518, p=0.003) and right HGS (ρ=0.387, p=0.035) in patients. When SI, DxLean, US-measured section of the distal third of the right rectus femoris, age and BMI were entered in a multiple regression model, SI was an independent predictor of right HGS (ß 0.27, p=0.033. SI may be a helpful surrogate marker to identify those CS patients who are more likely to show low muscle mass and strenght after remission. This work was supported by ISCIII (FIS PI14/0194 and PI17/00749), FEDER funds Unless otherwise noted, all abstracts presented at ENDO are embargoed until the date and time of presentation. For oral presentations, the abstracts are embargoed until the session begins. Abstracts presented at a news conference are embargoed until the date and time of the news conference. The Endocrine Society reserves the right to lift the embargo on specific abstracts that are selected for promotion prior to or during ENDO.