CSR Bone and Mineral Metabolism in CKD (CKD-MBD)

Question 1

What is the primary mechanism by which CKD leads to secondary hyperparathyroidism?

Accepted Answer

Phosphate retention reduces ionized calcium and directly stimulates PTH secretion

Answer

In CKD, reduced phosphate excretion causes hyperphosphatemia, which lowers ionized calcium and suppresses calcitriol production, both of which stimulate the parathyroid glands to secrete more PTH.

Question 2

Which form of vitamin D is synthesized by the kidney and considered the biologically active form used in CKD management?

Accepted Answer

Calcitriol (1,25-dihydroxyvitamin D)

Answer

Calcitriol (1,25-dihydroxyvitamin D) is produced by 1-alpha hydroxylase in the kidney and is the most potent active form; its synthesis is impaired in CKD, directly contributing to CKD-MBD.

Question 3

FGF-23 (fibroblast growth factor 23) rises early in CKD progression. What are its two primary effects on mineral metabolism?

Accepted Answer

Increases urinary phosphate excretion and suppresses renal calcitriol production

Answer

FGF-23 promotes phosphaturia by downregulating NaPi-2a/2c co-transporters and suppresses 1-alpha hydroxylase, reducing calcitriol synthesis, which collectively worsen secondary hyperparathyroidism.

Question 4

According to KDIGO 2017 guidelines, what is the recommended target for intact PTH (iPTH) in dialysis patients (CKD G5D)?

Accepted Answer

2–9 times the upper limit of normal

Answer

KDIGO 2017 recommends maintaining iPTH between 2 and 9 times the upper limit of normal in dialysis patients, balancing the risks of adynamic bone disease (over-suppression) against osteitis fibrosa (under-treatment).

Question 5

Which type of renal osteodystrophy is characterized by low bone turnover, reduced osteoblast and osteoclast activity, and is associated with over-suppression of PTH or aluminum toxicity?

Accepted Answer

Adynamic bone disease

Answer

Adynamic bone disease features minimal bone remodeling due to very low PTH levels or prior aluminum accumulation, increasing fracture risk and the risk of hypercalcemia from calcium loading.

(CSR) Board Certified Specialist in Renal Nutrition Practice Test

(CSR) Board Certified Specialist in Renal Nutrition Practice Test

CSR Bone and Mineral Metabolism in CKD (CKD-MBD)