PROK2 and obesity due to melanocortin 4 receptor deficiency: However, covariance analysis showed that children with obesity had elevated levels of fasting PK2 compared to the normal-weight controls (14937.2 ± 4073.6 vs. 11373.5 ± 3059.5 pg/mL, P < 0.001; Figure 1(b)) even after adjusting for sex.