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

Increased intestinal calcium absorption stimulates PTH release

Answer

Decreased sodium reabsorption triggers compensatory PTH release

Answer

Elevated calcitriol levels suppress calcium-sensing receptor activity

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

Ergocalciferol (vitamin D2)

Answer

Cholecalciferol (vitamin D3)

Answer

Calcidiol (25-hydroxyvitamin D)

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

Increases intestinal phosphate absorption and stimulates PTH secretion

Answer

Suppresses renal phosphate reabsorption and stimulates calcitriol synthesis

Answer

Stimulates osteoblast activity and reduces serum calcium

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

Normal range: 10–65 pg/mL

Answer

1–2 times the upper limit of normal

Answer

Greater than 10 times the upper limit of normal

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

Osteitis fibrosa cystica

Answer

Mixed uremic osteodystrophy

Answer

Osteomalacia

Question 6

The phosphorus-to-protein ratio (mg phosphorus per gram of protein) is an important counseling tool. Which protein source generally has the LOWEST phosphorus-to-protein ratio?

Accepted Answer

Egg whites

Answer

Processed cheese

Answer

Dark cola beverages

Answer

Whole milk

Question 7

In CKD patients, phosphorus from plant-based foods (e.g., legumes, grains) is generally absorbed at what rate compared to phosphorus from animal-based foods?

Accepted Answer

Lower rate — plant phosphorus is bound to phytate and requires phytase for release

Answer

The same rate — all dietary phosphorus is equally absorbed

Answer

Higher rate — plant enzymes release extra phosphorus

Answer

Not clinically relevant — only phosphate binder timing matters