Evaluation of bone and muscle composition and function in polycystic ovarian syndrome

Polycystic ovary syndrome (PCOS) is the most common endocrine disorder in women. Although its negative effects on many systems are known, potential effects of PCOS on the musculoskeletal system are not well established. In this study, we aimed to examine the effects of PCOS on muscle and bone composition and function in women in the late reproductive years. The study included 34 PCOS 32 age- and BMI-matched control women. To determine body composition, all subjects underwent dual energy x-ray absorptiometry (DXA). Furthermore, cross-sectional muscle areas and fat fraction of muscles were assessed by abdomen and thigh magnetic resonance imaging (MRI). Muscle strength was measured using an isokinetic dynamometer, Biodex® System Pro3 (Biodex Corp. Shirley NY, USA). Knee extensor and knee flexor concentric muscular strength was assessed at angular velocities of 60°/sec, which represents the amount of angular displacement per unit time. The mean age was 43 ± 3.7 yr in PCOS and 42.2 ± 3.5 yr in the controls. At the time of diagnosis, 94.1% (n=32) of PCOS patients were phenotype A, while 5.9% (n=2) were phenotype B. Testosterone, FAI and fasting insulin were higher in PCOS patients than controls (p<0.001, p=0.001 and p=0.032, respectively). While total abdominal muscle area (TAMA), paraspinal muscle area, thigh muscle area, visceral adipose tissue (VAT), subcutaneous adipose tissue (SAT), vertebral magnetic resonance imaging-proton density fat fraction (MRI-PDFF), thigh and paraspinal muscle MRI-PDFF were similar between groups, liver MRI-PDFF was higher in the PCOS group (p=0.044). This was mainly due to the difference in the non-obese population (p=0.029). There was no difference between the groups for DXA-derived muscle and bone composition. Subgroup analysis showed that obese PCOS patients had higher TAMA (p=0.012) and visceral adipose tissue (p=0.049) than obese controls. Although not reaching statistical significance, a trend towards increased visceral adipose tissue supporting truncal adiposity was found in the PCOS group (p=0.072). Composition parameters measured by MRI and DEXA for both PCOS patients and controls mainly correlated with BMI and fasting insulin values, but not with androgen levels. Isokinetic dynamometer analyses revealed higher normalized knee extensor peak torque in nonobese women than the obese group, however did not show a difference for muscle mechanical function between PCOS and controls other than increased 60°/sec knee extensor average power (W) in nonobese PCOS (p=0.049). Our results suggest increased liver adiposity in women with PCOS at late reproductive years. Obese PCOS women have higher abdominal muscle mass and visceral fat than obese controls. Muscle mechanical function in general is similar between PCOS and controls in late reproductive years.