Indeed, in vitro studies have reported a role for leptin in disc degeneration (Zhao et al., 2008; Samartzis et al., 2013; Segar et al., 2016), and leptin is proposed as a causative link between obesity and osteoarthritis (Hui et al., 2012; Vuolteenaho et al., 2014). The gene discussed is LEP; the disease is obesity due to melanocortin 4 receptor deficiency.