In an analysis from the Study for the Early Evaluation of chronic Kidney disease (SEEK) it is noted that the prevalence of secondary hyperparathyroidism (PTH over 65 pg/mL) starts to increase from CKD stage 3 and continues to increase all along the drop in the GFR, including practically all patients with a GFR below 20 mL/min 24. Here, PTH is linked to chronic kidney disease.