Phosphate Disorders Physiology Mnemonics Flashcards
What organs are involved in phosphate balance?
Bone, Kidney, Intestine
Bone stores 85% of phosphate, kidney excretes 700–900 mg/day, intestine absorbs 65% of dietary phosphate.
What is the main intestinal phosphate transporter?
NaPi-2B (Na/Pi-IIb)
It is primarily located in the duodenum and jejunum.
What stimulates NaPi-2B?
LOW
L: Low phosphate diet, O: 1,25(OH)₂D₃, W: Water.
What inhibits NaPi-2B?
Toxic AM
A: Arsenate, M: Mercury, T: Calcitonin.
What are the kidney phosphate transporters?
SLC34A1, SLC34A3, SLC20A2
SLC34A1 is Na/Pi-IIa (proximal tubule, electrogenic), SLC34A3 is Na/Pi-IIc (proximal tubule, electroneutral), SLC20A2 is PiT-2.
What is the role of PTH in phosphate regulation?
PTH Punishes Phosphate
It degrades transporters and decreases reabsorption.
What does FGF-23 do?
FGF-23 Flushes Phosphate
It decreases reabsorption and vitamin D levels.
What hormones control phosphate homeostasis?
PTH, FGF-23, Vitamin D
PTH breaks down bone, FGF-23 flushes phosphate, and Vitamin D increases gut absorption.
What are the causes of hypophosphatemia?
RAPID
R: Renal wasting, A: Alcoholism, P: Poor intake, I: Intestinal malabsorption, D: Diuretics.
What are the causes of hyperphosphatemia?
CRUSH
C: CKD, R: Rhabdomyolysis, U: Underactive PTH, S: Supplements, H: Hypervitaminosis D.
What types of phosphate binders are there?
C.M.A.
C: Calcium-based, M: Magnesium-based, A: Aluminum-based.
What is the mnemonic for phosphate distribution in the body?
B.O.N.E.S.
B: Bones (85%), O: Organophosphates (14%), N: NaPi transporters (1%), E: Excreted (700-900 mg), S: Secreted (200 mg).
What does the mnemonic D.J. PASS represent?
Intestinal Absorption Pathways
D: Duodenum, J: Jejunum, P: Passive (ileum), A: Arsenate inhibits, S: Stimulated by 1,25(OH)₂D₃.
What are the three NaPi transporters in the proximal tubule?
NaPi-IIa, NaPi-IIc, PiT-2
NaPi-IIa is SLC34A1, NaPi-IIc is SLC34A3, and PiT-2 is SLC20A2.
What does PTH do regarding NaPi transporters?
Degrades NaPi transporters
It reduces phosphate reabsorption.
What is the function of FGF-23?
Lowers renal Pi reabsorption
It works with Klotho and is elevated in CKD.
What does Vitamin D do in relation to phosphate?
Delivers phosphate
It increases gut absorption and elevates FGF-23.
What are the clinical disorders associated with hypophosphatemia?
3 R’s
R: Rickets/Osteomalacia, R: Renal wasting, R: Refeeding syndrome.
What mnemonic describes the effects of PTH on phosphate?
PTH DUMPS
D: Degrades transporters, U: Unleashes bone phosphate, M: Makes kidneys excrete phosphate, P: Pumps up calcium, S: Suppresses if Ca²⁺ high.
What are the phosphate transporters in the proximal tubule?
SLC34A1 (NaPi-IIa), SLC34A3 (NaPi-IIc), SLC20A2 (PiT-2)
Mnemonic: ‘SLC 34-1-2-3’
What does the mnemonic ‘2A vs 2C’ represent?
IIa: All segments (S1-S3), IIc: Central segments only (S1-S2)
Mnemonic: ‘2A vs 2C’
How many Na⁺ ions does NaPi-IIa transport?
3 Na⁺
Mnemonic: ‘3-2-1 Phosphate Ride’
How many Na⁺ ions does NaPi-IIc transport?
2 Na⁺
Mnemonic: ‘3-2-1 Phosphate Ride’
How many H₂PO₄⁻ ions does PiT-2 transport?
1 H₂PO₄⁻
Mnemonic: ‘3-2-1 Phosphate Ride’
What does PTH do to phosphate transporters?
Degrades transporters, endocytosis via PKA/PKC, stimulates bone resorption, targets NaPi-IIa first, reduces reabsorption, osteoclast activation, yields phosphaturia, sparing of calcium
Mnemonic: ‘PTH DESTROYS’
What is the role of FGF-23 in phosphate handling?
Lowers NaPi-IIa/IIc, upregulates phosphaturia, suppresses 1,25(OH)₂D₃, helped by Klotho, enhances renal excretion, skeletal origin
Mnemonic: ‘FGF-23 FLUSHES’
What are the causes of hypophosphatemia represented by the mnemonic ‘DROP’?
- Diuretics (chronic)
- Renal wasting (Fanconi)
- Osteomalacia (FGF-23 excess)
- Poor intake (alcoholism)
Mnemonic: ‘DROP’
What are the causes of hyperphosphatemia represented by the mnemonic ‘CRUSHED’?
- CKD
- Rhabdomyolysis
- Uremia
- Suppressed PTH
- Hypervitaminosis D
- Excess intake
- Drugs (bisphosphonates)
Mnemonic: ‘CRUSHED’
What does the mnemonic ‘PiT-2 Loves ACID’ indicate?
- Active at Acidic pH
- Ceases at Circumneutral pH
- Inhibited at Increased pH
- Divalent preference (but transports monovalent)
Mnemonic: ‘PiT-2 Loves ACID’
What does the mnemonic ‘PIN’ stand for in renal phosphate handling?
- Proximal tubule
- Inward (lumen→blood)
- Na⁺-dependent
Mnemonic: ‘PIN’
How can the kidney be visualized as a factory?
NaPi-IIa = Fast conveyor belt (3 workers/package), NaPi-IIc = Slow belt (2 workers/package), PiT-2 = Acid-loving robot (1 worker/package), PTH = Wrecking ball smashing belts, FGF-23 = Supervisor shutting down lines
Memory Palace Tip: Visualize the kidney as a factory
What is the overall effect of PTH on phosphate?
PTH sends phosphate to the urine (↓ reabsorption, ↑ excretion)
Mnemonic: “PTH – Phosphate To Heaven (urine)”
What does PTH block to reduce phosphate reabsorption?
PTH blocks Na/Pi cotransporters
Alternative mnemonic: “No PI (π) for PTH”
What are the receptor pathways activated by PTH?
A-B-C Pathways:
* A - Apical → PKC
* B - Basolateral → PKA
* C - Common outcome: Cotransporters degraded
Mnemonic: “A-B-C Pathways”
What does the mnemonic ‘PKC Ate, PKA Baked’ represent?
It represents the PTH receptor pathways:
* Apical → PKC
* Basolateral → PKA
Alternative mnemonic for receptor pathways
What is the role of NHERF1 in Na/Pi-IIa regulation?
PDZ domains in NHERF1 ‘park’ Na/Pi-IIa at the membrane
Mnemonic: “NHERF’s PDZ – Parking Zone for NaPi”
How does PTH affect Na/Pi-IIa?
PTH phosphorylates NHERF1, leading to internalization of Na/Pi-IIa
Alternative mnemonic: “Ezrin the Bridge, PTH the Quake”
What are some inhibitors of phosphate reabsorption?
Inhibitors include:
* Dopamine
* FGF-23
* Glucocorticoids
* PTH
* (Bonus: Acidosis, High phosphate, Diuretics)
Mnemonic: “Dopamine Fights Glucocorticoids, PTH, FGF”
What is included in PTH’s foe list?
Foes include:
* FGF-23
* Other hormones (dopamine, glucocorticoids)
* Expanded volume (↓ Na⁺ reabsorption)
* Low pH (acidosis)
Alternative mnemonic: “PTH’s Foe List”
What promotes phosphate reabsorption?
Promoters include:
* Volume contraction
* Insulin
* Parathyroidectomy
* Growth hormone
* Hypermagnesemia
Mnemonic: “Calcitriol’s VIP Guests”
What does the mnemonic ‘G.I. Protect Phosphate’ refer to?
It refers to promoters of phosphate reabsorption:
* Growth hormone
* Insulin
* Parathyroidectomy
* Phosphate restriction
Alternative mnemonic for promoters
What is a quick summary of PTH’s effect on NaPi?
PTH Kicks NaPi Out:
* PKC/PKA pathways
* Target NHERF1/ezrin
* Hurls Na/Pi-IIa to lysosomes
* Kidney excretes phosphate!
Mnemonic: “PTH Kicks NaPi Out”
What does FGF-23 do to phosphate levels?
Blocks phosphate (↓ Na/Pi-IIa)
FGF-23 is responsible for lowering phosphate levels in the body.
How does FGF-23 affect calcitriol?
Opposes calcitriol (↓ 1α-hydroxylase)
FGF-23 inhibits the enzyme responsible for activating vitamin D.
What is the effect of FGF-23 on PTH secretion?
Negates PTH (↓ secretion)
FGF-23 reduces the secretion of parathyroid hormone.
What is the role of FGF-23 in phosphate excretion?
Excretes phosphate (↑ urine)
FGF-23 increases phosphate excretion through urine.
What is the skeletal origin of FGF-23?
Skeletal origin (osteocytes)
FGF-23 is produced by osteocytes in the bones.
What does Klotho do in relation to FGF-23?
Required for FGF-23 to work
Klotho acts as a cofactor necessary for the function of FGF-23.
What are the two forms of Klotho?
- Key (transmembrane - cofactor)
- Lone (secreted - independent action)
Klotho has both a membrane-bound form and a secreted form that can function independently.
What does the FGF-23 activation pathway involve?
- FGFR binds FGF-23
- Includes Klotho
- Results in ERK activation
- Ends with NHERF1 phosphorylation → ↓Na/Pi-IIa
This pathway is crucial for the action of FGF-23 in regulating phosphate levels.
How is FGF-23 regulated by phosphate levels?
- Phosphate ↑ → FGF-23 ↑
- Osteocytes make it
- PTH stimulates release
Increased phosphate levels lead to higher production of FGF-23.
What clinical condition is associated with increased FGF-23?
Tumor-induced osteomalacia (↑FGF-23)
This condition is characterized by excessive production of FGF-23, leading to bone disease.
What is the effect of FGF-23 on vitamin D activation?
Inhibits vitamin D activation
FGF-23 reduces the activation of vitamin D, impacting calcium absorption.
What condition does FGF-23 cause in terms of phosphate levels?
Causes hypophosphatemia
FGF-23 leads to lower phosphate levels in the blood.
What is the relationship between Klotho and FGF-23?
Klotho-dependent
The action of FGF-23 is dependent on the presence of Klotho.
How does FGF-23 compare to PTH in phosphate regulation?
- FGF-23 lowers phosphate
- Inhibits both calcitriol and PTH
- PTH increases calcitriol (opposite effect)
FGF-23 and PTH have opposing actions on phosphate and vitamin D metabolism.
What mnemonic phrase helps recall FGF-23’s mechanism?
First Get Free (FGF) 23 cents to call KLOTHO long-distance to ERASE phosphate
This phrase aids in remembering the relationship between FGF-23 and Klotho in phosphate regulation.
What does the mnemonic ‘CALM DAD’ represent in dietary phosphate regulation?
Hypophosphatemia response:
* C: Ca²⁺ increases (inhibits PTH)
* A: Alpha-hydroxylase activates
* L: Lots of Mighty calcitriol (1,25(OH)₂D₃)
* M: Decreased PTH
* D: Absorption up
* A: Decreased excretion
* D:
What does the mnemonic ‘FURY MOM’ represent in dietary phosphate regulation?
Hyperphosphatemia response:
* F: FGF-23 spikes
* U: Unchecked PTH (due to low Ca²⁺)
* R: Reduced calcitriol
* Y: Yes to wasting (excretion)
* M: More PTH
* O: Output phosphate
* M: Maintain balance
What is the role of PTH in the ‘PTH vs FGF-23: The Sibling Rivalry’ mnemonic?
PTH (older sibling):
* Wants calcium (↑Ca²⁺ reabsorption)
* Dumps phosphate (↓NaPi-IIa)
What is the role of FGF-23 in the ‘PTH vs FGF-23: The Sibling Rivalry’ mnemonic?
FGF-23 (younger sibling):
* Controls phosphate (↑excretion via ↓NaPi-IIa)
* Turns off vitamin D (↓calcitriol)
What does the mnemonic ‘BONEY KID’ summarize?
Key pathways in phosphate regulation:
* B: Bone makes FGF-23
* O: Osteocytes sense phosphate
* N: NaPi-IIa downregulated
* E: Excretion occurs
* Y: Your kidneys balance it
* K: Klotho required
* I: Intestine absorbs less (when FGF-23 high)
* D: Vitamin D controlled (calcitriol regulation)
What key points are covered in the mnemonic ‘PHOS PHATE’?
Clinical connection:
* P: PTH - Phosphate excreter
* H: High phosphate? FGF-23 activates
* O: Osteocytes are sensors
* S: Serum levels tightly controlled
* P: Phosphate binders used in CKD
* H: Hypophosphatemia? Calcitriol helps
* A: Alpha-hydroxylase key enzyme
* T: Tubular reabsorption variable
* E: Excretion matches intake
What does the quick recall acronym ‘3P Balance’ stand for?
Quick responders in phosphate regulation:
* P: PTH
* P: Phosphate sensors (bone)
* P: Pathways (FGF-23/Klotho)
Fill in the blank: The visual mnemonic shows that [DIET] leads to [GUT] and is influenced by _______.
[1,25D]
True or False: The visual storytelling in the mnemonics uses family analogies.
True
What anatomical structures are involved in the phosphate regulation pathways?
Structures involved:
* Gut
* Bone
* Kidney
* Parathyroid
What is the significance of Klotho in phosphate regulation?
Klotho is required for phosphate excretion and regulation
