Between hyperfiltration and impairment: Demystifying early renal functional changes in diabetic nephropathy

Renal functional changes in diabetic nephropathy conventionally have been linked to progression of urinary albumin excretion. This paradigm was based on historic evidence noting that hyperfiltration occurred in the setting of normoalbuminuria and microalbuminuria and that loss of renal function began in the context of proteinuria. More contemporaneous research findings, using serum cystatin-C-based estimates of glomerular filtration rate (cC-GFR), have challenged this paradigm. Rather, the process of renal function loss appears to begin prior to the onset of proteinuria. In the 2nd Joslin Kidney Study on the Natural History of Microalbuminuria, over one-third of type 1 diabetes (T1DM) patients with microalbuminuria at the time of enrollment already had evidence of mild (cC-GFR