While female OT null mice also develop adult onset obesity (Camerino, 2009; Tamma et al., 2009) as early as 8 weeks (Tamma et al., 2009), female OTR deficient mice fail to develop increased body weight relative to control counterparts (Takayanagi et al., 2008; Sun et al., 2019). The gene discussed is OXTR; the disease is obesity due to melanocortin 4 receptor deficiency.