PTH and chronic kidney disease: Taking stage 4 as an example, assuming a men aged 45 years old (20 points) with serum calcium of 8 mg/dL (25 points), inorganic phosphorus of 6 mg/dL (42 points), intact parathyroid hormone of 100 pg/mL (20 points), the probability of having stage 4 CKD was estimated to be 90%.