Tissue fat quantification by magnetic resonance imaging: proton density fat fraction in polycystic ovary syndrome.

Research Question: What are the potential differences between lean women with and without polycystic ovary syndrome (PCOS) in fat content in liver, vertebrae, paraspinal muscles, pancreas, subcutaneous (SCAT) and visceral adipose tissue (VAT)? Magnetic resonance imaging proton density fat fraction (PDFF) was used to establish these differences. This is a novel, non-invasive, operator-independent method with comparable diagnostic sensitivity and specificity to histologic examination for fatty liver disease, and strong correlation with muscle strength in neuromuscular studies.

Design: Twenty lean women with PCOS (mean age 23.9 ± 2.3; body mass index [BMI] 22.4 ± 2.0) and 20 age- and BMI-matched healthy women (mean age 24.9 ± 1.5; BMI 21.5 ± 1.9) were enrolled in this cross-sectional study. Anthropometric, biochemical and hormonal evaluations along with magnetic resonance imaging proton density fat fraction were carried out.

Results: PDFF% measurements of liver, SCAT and VAT were higher in the PCOS group, indicating increased fat content in these areas in lean women with PCOS compared with controls (P = 0.045, 0.030 and 0.037, respectively). In contrast, PDFF% values of vertebrae and paraspinal muscles in the PCOS group were lower than controls (P = 0.038 and 0.05, respectively). Pancreatic PDFF% measurements were similar between the groups. In the PCOS group, PDFF% of VAT was positively correlated with free androgen index (r = 0.69, P = 0.002).

Conclusions: PDFF% measurement, an MRI-based novel biomarker, reveals increased fat in liver, SCAT and VAT, and decreased fat in vertebral bones and paraspinal muscles of lean women with PCOS.