PTBP2 and obesity due to melanocortin 4 receptor deficiency: Genotype distributions were not related to drop-out rates except for ETV5 and FAIM2, which had more completers among homozygotes than among non-carriers of the obesity risk-allele (P = 0.01 and 0.02 respectively), and for PTBP2, which showed the opposite pattern (P = 0.03).