Combined with our previous study showing that ten-week-old Col4a3−/− mice receiving a low-phosphate diet exhibit reduced serum phosphate levels and show no signs of skeletal muscle atrophy [5], our current study suggests that hyperphosphatemia is a pathologic factor that, on its own as well as in the context of CKD, might contribute to skeletal muscle atrophy. This evidence concerns the gene COL4A3 and hyperphosphatemia.