Lecture 13: TBL Ca Phosphate Acid Base Flashcards
List the major inputs and outputs of calcium and phosphate to and from plasma
Inputs =
GI absorption
Bone restoration
Outputs =
Urinary excretion
Bone mineralization (deposition)
List the 3 main hormones involved in the regulation of Ca and phosphate, identifying their major site of synthesis
PTH = parathyroid glands
Calcitriol = kidneys
FGF23 = bone
Describe the effects of PTH on Ca and Pi
Absorption = n/a
Excretion:
Ca = inc. reabsorption in DCT + dec. excretion
Pi = dec. reabsorption in PT + inc. excretion
Describe effect of calcitriol on Ca and Pi
Excretion = n/a
Absorption = inc. absorption of calcium and phosphate
Describe effects of FGF23 on Ca and Pi
Absorption = n/a
Excretion = dec. phosphate reabsorption in PT = inc. excretion
No effect on calcium!!
What are calcitropic hormones?
PTH + calcitriol
Direct relationship with calcium
What are phosphaturic hormones?
PTH and FGF23
Both have indirect relationship with phosphate
What do each hormone effect?
PTH = urinary excretion
calcitriol = GI absorption
FGF23 = urinary excretion
What is a pneumonic for PTH?
PTH
Protects plasma calcium
THwarts phosphate rich diet
What is PTH’s effect on calcium and phosphate?
Inc. calcium
Dec. phosphate
What is a pneumonic for calcitriol?
Calcitriol rhymes with skeletal
Provides calcium and phosphate for bone
What effects does calcitriol have on calcium and phosphate?
Inc. calcium
Inc. phosphate
What is a pneumonic for FGF23?
ForGet ‘Fosphate’
What effect does FGF23 have on calcium and phosphate?
Calcium = n/a
Dec. phosphate
What effects does PTH have on urinary excretion of calcium and phosphate?
Inc. Ca reabsorption in DCT = dec. excretion
Dec. phosphate reabsorption in PT = inc. excretion
What effect does FGF23 have on phosphate excretion?
Dec. phosphate reabsorption in PT = inc. excretion
What is the form of calcium that gets regulated??
Ionized!
Does NOT include calcium bound to albumin or complexed with anions
What is the indirect effect of phosphate on PTH secretion?
Inc. phosphate = Dec. ionized calcium = Inc. PTH secretion
Explain limitations of using plasma Ca concentration measured by clinical labs when discussing regulation of calcium and phosphate
Clinical labs measure TOTAL plasma calcium = can be misleading!
Inc. phosphate = dec. ionized Ca (but the total Ca would be unchanged)
Total plasma calcium can change even if ionized Ca remains constant
(Ex: if [albumin] changes)
What is the effect of inc. ionized calcium on PTH, calcitriol, FGF23 secretion?
PTH = dec.
Calcitriol = dec.
FGF23 = n/a
What is the effect of inc. phosphate on secretion of PTH, calcitriol and FGF23?
PTH = inc.
Calcitriol = dec.
FGF23 = inc.
What is the effect of dec. plasma calcium on
Calcitriol Ca IN (GI absorption) Ca OUT (excretion) Pi IN (GI absorption) Pi OUT (excretion)
Dec. plasma Ca =
Inc. calcitriol
Inc. Ca absorption
No change excretion
Inc. Pi absorption
No change excretion
What is the effect of dec. plasma calcium on
PTH Ca IN (GI absorption) Ca OUT (excretion) Pi IN (GI absorption) Pi OUT (excretion)
Dec. plasma Ca =
Inc. PTH
No change Ca absorption
Dec. Ca excretion
No change Pi absorption
Inc. Pi excretion
What are the effects of inc. plasma phosphate on
Calcitriol Ca IN (absorption) Ca OUT (excretion) Pi IN (absorption) Pi OUT (excretion)
Inc. plasma phosphate =
Dec. calcitriol
Dec. Ca IN
No change Ca excretion
Dec. Pi IN
No change Pi OUT
What is the effect of increased plasma phosphate on
PTH Ca IN (absorption) Ca OUT (excretion) Pi IN (absorption) Pi OUT (excretion)
Inc. plasma Pi =
Inc. PTH
No change Ca IN
Dec. Ca excretion
No change Pi IN
Inc. Pi excretion
What is the effect of increased plasma phosphate on
FGF23 Ca IN (absorption) Ca OUT (excretion) Pi IN (absorption) Pi OUT (excretion)
Inc. plasma Pi =
Inc. FGF23
No change Ca IN
No change Ca OUT
No change Pi IN
Inc. Pi excretion
What are the effects of PTH on secretion of other hormones?
PTH helps the other hormones
Inc. calcitriol
Inc. FGF23
What are the effects of calcitriol on secretion of other hormones?
calcitriol “calculates”: rejects help from PTH but needs FGF to avoid Pi overload
Dec. PTH
Inc. FGF23
What are the effects of FGF23 on secretion of other hormones?
FGF23 forgets the other hormones
Dec. calcitriol
Dec. PTH
Describe the two important roles of the kidney in the regulation of acid-base balance
- Reabsorption of filtered bicarbonate
2. Synthesis of new bicarbonate
Explain why the kidney cannot eliminate the fixed metabolic acid load by excreting H+
(instead of making 70-100 mmol of new bicarbonate every day)
Kidney can ONLY excrete 0.04 mmol of H+ per day - NOT 70-100 mmol!!!
List the 4 major acid-base disorders
Metabolic acidosis
Respiratory acidosis
Respiratory alkalosis
Metabolic alkalosis
What is a normal level for P(CO2) in mmHg?
[HCO3] in mmol/liter?
P(CO2) = 40
[HCO3] = 24
How do you determine type of acid-base disorder?
(1) look at pH
- if <7.38 = acidosis
- if >7.42 = alkalosis
(2) look at P(CO2)
Acidosis:
- if <40 mmHg = metabolic acidosis
- if >40 mmHg = respiratory acidosis
Alkalosis:
- if <40 mmHg = respiratory alkalosis
- if >40 mmHg = metabolic alkalosis
What is the ‘rule’ to distinguish between acute vs. chronic respiratory acidosis?
If ACUTE:
Every 2 mmHg increase in P(CO2) = 0.01 unit dec. in pH
What is the ‘rule’ to distinguish between acute vs. chronic respiratory alkalosis?
If ACUTE:
Every 1 mmHg dec. in P(CO2) = 0.01 unit inc. in pH
Identify important causes of metabolic acidosis
Kidney disease
Uncontrolled DM
Anaerobic exercise
Methanol toxicity
CA inhibitors
K+-sparing diuretics
Identify important causes of ACUTE respiratory acidosis
Acute opioid or barbiturate OD
Identify important causes of CHRONIC respiratory acidosis
COPD
Identify important causes of ACUTE respiratory ALKalosis
Acute hyperventilation due to anxiety
Identify important causes of chronic respiratory ALKalosis
High altitude
For >48-72 hours
Identify important causes of metabolic alkalosis
Vomiting
Hyperaldosteronism
Loop diuretics
Thiazides diuretics
