Nevertheless, cystatin C-based eGFR estimates can also be subject to error because the serum levels of cystatin C are confounded by extrarenal factors such as age, gender, body mass, body length, cigarette smoking, high low-density lipoprotein cholesterol, low high-density lipoprotein cholesterol, obesity, diabetes, and inflammation [24,25]. Here, CST3 is linked to obesity due to melanocortin 4 receptor deficiency.