CKD MBD Flashcards
What is FGF-23?
Fibroblast growth factor 23
One of the earliest markers of CKD progression
Not typically measured or used in clinical practice
Produced by osteoblasts in response to increases in serum phos and acts on kidneys and parathyroid glands
*Stimulates urinary phos excretion within renal proximal tubules
*Inhibits 1-a-hydroxylase activity –> prevents conversion of 25-hydroxyvitamin D to 1,25-dihydroxyvitamin D (theoretically reduces intestinal phos absorption).
*Increases calcium reabsorption within distale tubules.
What is klotho?
Co-receptor for FGF-23
Helps FGF-23 more readily bind to FGF receptor in kidney
Expression is inhibited in CKD resulting in resistance to FGF-23, reduced phos excretion in urine, reduced inhibition of PTH excretion
What is the strongest predictor for risk of heart disease and death in CKD?
Vascular calcification
What is calciphylaxis?
Ischemic small-vessel vasculopathy
Risk factors: elevated Ca/P, use of Ca-based binders, Vit D therapy, SHPT, females, White people, obesity, diabetes, low alb, trauma.
Correlated with warfarin therapy
What are the components of total serum calcium?
Ionized (48%); protein bound (46%), complexed fractions (7%) bound to other molecules like citrate and phosphate
Does not reflect total body calcium
What influences calcium absorption?
PTH and calcitriol, calcium concentration, fluid shifts, metabolic acidosis or alkalosis, diuretic use
What are the calcium recommendations in 2020 KDOQI guidelines?
CKD 3-4: 800-1000 mg/day if not on vit D analogs
CKD 5D: avoid hypercalcemia
What are the phosphorus recommendations in 2020 KDOQI guidelines?
Maintain serum levels WNL
Consider bioavailability of sources
What are the vitamin D management recommendations in 2020 KDOQI guidelines?
Suggest chole or ergo to correct deficiency or insufficiency
What are the optimal PTH recommendations in 2020 KDOQI guidelines?
None
Where is the majority of phos absorbed?
Jejunum and ileum via paracellular passive absorption and rate-limiting sodium-phos cotransporters (60%)
Remaining 40% of phos is unabsorbed and excreted in feces.
What are things to know about sevelamer?
Ion exchange polymer, interacts with phos in the GI tract
Bile acid sequestrant, may provide cardioprotective benefit by reducing LDL and total cholesterol
May bind bile acids and interfere with absorption of fat soluble vitamins.
Not recommended with recent history of GI surgery
What are things to know about calcium-based binders?
Ca Citrate discouraged due to risk of increased aluminum absorption and potential side effects
Ca Carbonate has higher elemental calcium content, less binding when used with PPI or H2 inhibitors
Ca Acetate is more dissolvable than CaCO3
What are things to know about lanthanum carbonate (Fosrenol)?
Phos binding capacity may decrease at higher doses
No evidence of accumulation in bone, toxicity, or liver damage after 5 years
What are things to know about sucroferric oxyhydroxide (Velphoro)?
500 mg elemental iron
Claims to bind up to 130 mg phos/tablet
Low rate of iron absorption
