Thigh muscle fat infiltration is associated with impaired physical performance despite remission in Cushing's syndrome.

OBJECTIVES: To quantify the degree of fatty infiltration in the thigh muscles of "cured" CS patients and evaluate the relationship between intramuscular fatty infiltration and physical performance.

DESIGN: This was a cross-sectional study.

SETTING: Tertiary referral center.

PATIENTS: Thirty-six women with CS in remission, and 36 controls matched for age, BMI, menopausal status, and level of physical activity.

MAIN OUTCOME MEASURES: We analyzed the percentage fat fraction [FF] of the thigh muscles in the anterior, posterior, and combined anterior and posterior compartments using MRI, 2-point Dixon sequence. We assessed muscle function and strength using the following tests: Gait Speed Velocity (GS), Timed Up and Go (TUG), 30-Second Chair Stand and Hand Grip Strength.

RESULTS: FF in all the compartments analyzed was increased in patients as compared with controls. Performance on TUG, 30-seconds chair stand and GS was more impaired in CS patients vs. controls. In patients, greater FF was negatively associated with performance on functional tests. FF in the combined anterior and posterior compartments predicted performance on TUG (ß .626, p<0.000) and GS (ß -.461, p=0.007), after adjusting for age, BMI, menopausal status and muscle mass.

CONCLUSIONS: Thigh muscle fatty infiltration is increased in "cured" CS patients, and associated with poorer muscle performance. Future studies are needed to establish therapeutic strategies improving muscle weakness in these patients.