Further sensitivity analyses confirmed that association estimates between obesity measures and measures of kidney function remained largely unaffected by inclusion/exclusion of genetic variants mapping onto genes related to metabolism of creatinine/cystatin C/BUN (Supplementary material online, Table S3) and that there is no evidence for bidirectional causality between obesity measures and kidney function (Supplementary material online, Table S8). The gene discussed is CST3; the disease is obesity due to melanocortin 4 receptor deficiency.