In Fanconi syndrome, the megalin-receptor-mediated endocytosis of LMWPs is disturbed, resulting in the increased excretion of albumin, prealbumin (transthyretin, 55 kDa), α1-acid glycoprotein (40 kDa), and other LMWPs (Figure 1). This evidence concerns the gene TTR and Fanconi renotubular syndrome.