MET EOYS4 Flashcards
What effect does increasing FGF23 have on:
Serum phosphate levels [1]
Phosphate excretion [1]
1a hydroxylase activity [1]
High FGF23:
* increase fractional phosphate excretion
* Reduce serum phosphate levels
* Reduce 1α-hydroxylase activity
Which of the following secretes FGF-23
osteoblast
osteoclast
chondrocyte
osteocyte
Which of the following secretes FGF-23
osteoblast
osteoclast
chondrocyte
osteocyte
Explain what happens when have hypercalcemia and diabetes? [2]
Nephrogenic Diabetes Insipidus:
* Ca2+ binds to CaSR in nephrone, which down regulates NaKCL2 symporter
* Renal stones & Renal failure due to XS Ca2+ in urine
Parathyrodism diagnosis
Explain the mechanism of a MIBI scan [1]
The parathyroid scan uses the radioisotope, technetium-99m sestamibi (or MIBI), which is injected into the body and absorbed by the overactive parathyroid mitochondria.
State the vertebral levels for each of the following:
Iliohypogastric [1]
Ilioinguinal [1]
Genitofemoral [1]
Iliohypogastric: L1
Ilioinguinal: L1
Genitofemoral; L1 & L2
Which type of diuretic may be used to treat kidney stones?
Loop diuretics
Thiazide like diuretics
K sparing diuretics
Carbonic anhydrase inhibitors
Which type of diuretic may be used to treat kidney stones?
Loop diuretics
Thiazide like diuretics: cause hypercalcemia
K sparing diuretics
Carbonic anhydrase inhibitors
Which areas of nephron cause reabsorbtion of Ca2+ dependently / independently of PTH? [3]
PCT: independent
LoH: independent
DCT: PTH dependent
Explain how Ca2+ is reabsorbed at PCT [2]
At PCT:
- independent of PTH
- Driven by NaKCl2 channel causing a voltage gradient paracellularly which Ca2+ flows (coupled with Na+ reabsorbtion)
Explain how Ca2+ is reabsorbed at LoH [2]
Driven by voltage gradient: Para/transcellular
Coupled with Na+ reabsorbtion: NKCC2 channel
Why do thiazide diuretics raise serum calcium?
Increase Ca2+ reabsorbtion into the blood / raises Ca2+ serum levels:
- Blocks Na/Cl symporter on luminal side
- This drops the Na conc. In tubular cell
- This creates Na diffusion gradient
- Na diffusion increases from capillary into tubular
cell - across Na/Ca exchanger -> takes Na into cell and transports Ca2+ into blood. -> increase in blood Ca levels.
The conversion of vit. D to WHAT is regulated? [1]
The conversion of vit. D to WHAT is unregulated? [1]
What are the enzymes used for each? [2]
Conversion of vit D to 25(OH)D in the liver is an unregulated process, under the action of p450 enzymes. The half life of 25(OH)D is 2-3 weeks.
The conversion of vit D to 1,25(OH)D is highly regulated, via 1αhydroxylase
How does negative feedback of activation of vitamin D receptor work?
In most cells there is a negative feedback inhibition: activation of the VDR inhibits the action of 1α hydroxylase (which converts vit D to active form), therefore reducing the amount of activated vitamin D able to bind to the VDR.
Why would chronic infection (e.g from sarcoidosis / TB granuloma) cause hypercalcemia?
- Macrophages produce vitamin D
- Release of vitamin D is converted to 1 25 dihydroxyvitamin dby 1α hydroxylase
- Causes increase in serum calcium
What does the hormone FGF23 do? [1]
Which cells are they secreted from? [1]
What does FGF23 do to 1-a-hydroxylase? [1]
What does the hormone FGF23 do? [1]
Reduces serum P levels USED FOR WHEN GET P EXCRETED FROM FROM BONE BUT NEED TO EXCRETE VIA RENAL SYSTEM
It inhibits renal tubular reabsorption of phosphate
Which cells are they secreted from? [1]
Secreted by osteocytes
What does FGF23 do to 1-a-hydroxylase? [1]
reduces 1-a-hydroxylase: less activated vit. D
Explain 3 classes of symptoms seen in hypercalcemia
Hypercalcemia
Symptoms
Neuropsychiatric disorders: due to reduced membrane excitibility causing reduced nerve transmisison in the brain
GI abnormalities:
* Constipation / pancreatitis: reduced membrane excitibility causes less muscle contraction
Renal dysfunction:
* Nephrogenic Diabetes Insipidus: Ca2+ binds to CaSR in nephrone, which down regulates NaKCL2 symporter
Renal stones & Renal failure due to XS Ca2+ in urine
How do you treat hypercalcemia?
Expand plasma volume IV saline: reduces voltage gradient in tubular cells -> less Ca ++ reabsorbed
Reduce Ca release from bone
Treat underlying cause
What are primary, secondary and tertiary causes of hyperparathyroidism?
Primary: Parathyroid adenoma/carcinoma/hyperplasia
Secondary: Physiological compensation for hypocalcemia or Vitamin D deficiency. Can create tertiary
Tertiary: Autonomous PTH production following chronic secondary.
How can you ID if have primary Hyperparathyroidism? [4]
Neck USS
MIBI scan
CT scan
Parathyroid Venous Sampling
kidney, [] converts 25-hydroxyvitamin-D into 1,25-dihydroxyvitamin-D
kidney, 1-α-hydroxylase converts 25-hydroxyvitamin-D into 1,25-dihydroxyvitamin-D
Label A-E
A: Renal artery
B: Segmental arteries
C: Interlobar arteries
D: Arcuate arteries
E: Interlobal arteries
What are the 3 main nerves associated with the kidney? [3]
Iliohypogastric
Ilioinguinal
Genitofemoral