Endocrine Abstracts

Background: Proton-density fat fraction (PDFF), derived from chemical shift encoding-based water-fat magnetic resonance imaging, has emerged as an important surrogate method for calculation of fat composition in a number of tissues including liver, vertebrae and muscles. This study aims to determine whether fat composition of these tissues, as well as visceral and subcutaneous adiposity differ between women with PCOS and healthy controls.

Methods: 17 lean women with PCOS (age: 21.4±3.1 years, BMI: 22.1±1.9 kg/m²) and 16 healthy women who were matched for age, BMI and waist circumference (P=0.56, 0.12 and 0.11 respectively) were included. The diagnosis of PCOS was based on Rotterdam criteria. Hormonal and biochemical evaluations and MRI-based PDFF measurements were performed in all participants. Radiologists reporting MRI examinations were blinded to clinical data and patient control status.

Results: PDFF% values of liver were higher (median 4.5% vs. 3.6%, P=0.02) whereas PDFF% values of both vertebrae and paraspinal muscles were lower (32.8% vs. 41.6%; and 12.8% vs 15.1%, P<0.05 for both) in PCOS patients than controls. Also, subcutaneous and visceral adipose tissue areas were increased in PCOS patients compared to healthy women (median 32.8 cm² vs. 18.5 cm², and 112.9 cm² vs. 83.1 cm², P<0.05 for both). Pancreas PDFF% values were similar between the groups. Visceral and subcutaneous fat area measurements were positively correlated with FAI (r=0.71, P<0.01 and r=0.49, P<0.05 respectively). Subcutaneous fat area was also positively correlated with fasting insulin (r=0.54, P<0.05) and 2 h insulin during OGTT (r=0.78, P<0.01). PDFF% of liver in PCOS did not show a correlation with insulin resistance or lipid parameters but there was a trend for positive correlation with free androgen index (FAI) (r=0.37, P=0.08).

Conclusions: Fat composition of liver calculated by PDFF with MRI, subcutaneous and visceral adipose areas are higher in lean PCOS patients than age, BMI and WC-matched healthy women. Biochemical androgen excess and insulin resistance are among the factors modulating intraabdominal adiposity in lean PCOS. Whether decreased PDFF measurements of vertebra and paraspinal muscles in the syndrome are related to muscle or bone strength remains to be determined.