C1QTNF3 and obesity due to melanocortin 4 receptor deficiency: However, research in human subjects has been equivocal, with total circulating CTRP3 levels reported to be reduced (Ban et al., 2014; Deng et al., 2015; Qu et al., 2015; Tan et al., 2013; Wolf et al., 2015) or elevated (Choi et al., 2014, 2012) with metabolic conditions such as obesity and/or metabolic syndrome.