Fig 1. Correlation of monozygotic within-pair differences in MIC-1/GDF15 serum levels and within-pair differences in BMI.

Correlation between within twin-pair difference in serum MIC-1/GDF15 levels and within twin-pair difference in BMI (n = 72 twins), performed by Spearman regression, identifies a highly significant correlation. In general the twin of the twin pair with a higher serum MIC-1/GDF15 level generally had a lower BMI than their identical twin pair. The reverse was also true.