MPZL3 and obesity due to melanocortin 4 receptor deficiency: While the relevance of MPZL3 to human obesity has yet to be reported in the literature, two genetic linkage studies have demonstrated that the MPZL3 chromosomal location (11q23.3) is associated with body mass (Hanson et al., 1998; Lindsay et al., 2001) and energy expenditure (Norman et al., 1998) in Pima Indians, an indigenous population displaying extremely high incidences of obesity and type 2 diabetes mellitus (Knowler et al., 1978, 1991).