PRG4 and obesity due to melanocortin 4 receptor deficiency: BMI-predictive proteins included established obesity markers and obesity-related proteins, including adiponectin, CRP, IGFBP1, IGFBP2, PRG4, SHBG, apolipoproteins (APOA4, APOF) and inflammatory response proteins (A2M, APCS, LBP, HSPG2, HP, AOC3, ITGB1, VNN1).