Role of the Kidney in Calcium and Phosphate Homeostasis

A comprehensive set of flashcards covering the role of the kidney in calcium and phosphate homeostasis, aimed at enhancing understanding and retention of essential concepts related to this topic.

What regulates total body calcium and phosphate levels?

Coordinated activity of the gastrointestinal tract, bone, and kidneys.

What percentage of total body calcium and phosphate is found in the extracellular fluid?

Approximately 1%.

Where is the majority of calcium reabsorbed in the kidney?

In the proximal tubule, TALH, and distal tubule.

What hormone increases calcium reabsorption in the kidney?

Parathyroid hormone (PTH).

Why are calcium-forming kidney stones treated with thiazides?

Thiazides increase sodium excretion and reduce calcium concentration in the distal nephron.

Where is most filtered phosphate reabsorbed?

In the proximal tubule.

What effect does PTH have on phosphate reabsorption?

PTH inhibits phosphate reabsorption.

What is chronic kidney disease associated with regarding parathyroid hormone?

Secondary hyperparathyroidism and decreased calcitriol formation.

What is calcitriol?

1,25(OH)2 Vitamin D, activated in the kidney.

What percentage of filtered calcium is reabsorbed in the proximal tubule?

65-70%.

What type of transport primarily occurs for calcium reabsorption in the proximal tubule?

Passive, paracellular transport.

What triggers the calcium reabsorption in TALH?

Positive transepithelial potential difference generated by potassium cycling.

What is the role of calcitonin in calcium reabsorption?

Calcitonin increases calcium reabsorption in TALH and distal tubule.

What happens to calcium reabsorption when plasma calcium levels are high?

High plasma calcium inhibits calcium reabsorption in TALH.

What does furosemide do in relation to calcium?

It inhibits calcium reabsorption in the TALH.

What contributes to the formation of calcium kidney stones?

Insolubility of calcium salts in the urinary tract.

What is phosphaturia?

Increased phosphate excretion due to PTH action.

What is the primary mechanism for phosphate reabsorption in the proximal tubule?

Secondary active cotransport with sodium.

How does acidosis affect urinary phosphate excretion?

It increases urinary phosphate excretion.

What dietary component impacts phosphate homeostasis?

Dietary phosphate absorption.

What effect does calcitriol have on phosphate levels?

Increases phosphate reabsorption.

What is a nonreabsorbable anion in the collecting duct?

Phosphate.

What is the relationship between chronic kidney disease and phosphate levels?

Chronic kidney disease leads to increased plasma phosphate levels.

What treatment is indicated for elevated plasma phosphate in kidney disease?

Low phosphate diet and phosphate binders.

How does PTH affect phosphate Tmax?

PTH lowers Tmax, reducing phosphate reabsorption.

What is the primary site of calcium reabsorption regulation?

TALH and distal tubule.

What physiological role does phosphate play in the body?

Buffering and as a constituent of macromolecules.

What type of signaling does calcium participate in?

Intracellular signaling.

How much phosphate is typically absorbed from the diet?

Approximately 1400 mg.

What are the main components of calcium homeostasis?

Diet, gut absorption, bone and kidney regulation.

What is the plasma phosphate concentration?

Approximately 1 mM.

What does chronic kidney disease do to calcitriol levels?

It decreases calcitriol formation.

What effect does PTH have on phosphate concentration in the kidney?

It increases phosphate excretion.

Where do calcium ions primarily exist in the body?

99% in ICF/bone.

What physiological functions does calcium contribute to?

Bone health, muscle function, and nerve signaling.

What happens to calcium reabsorption when sodium is reabsorbed?

Calcium reabsorption increases.

What type of calcium excretion is primarily regulated by the kidneys?

Renal calcium excretion.

What role does the gastrointestinal tract play in calcium homeostasis?

It contributes to dietary calcium absorption.

What is the range for total plasma calcium concentration?

Approximately 10 mg/dl.

What happens to PTH levels in chronic kidney disease?

PTH levels increase due to suppressed calcium levels.

Why is phosphate reabsorption in the collecting duct minimal?

It's considered a nonreabsorbable anion.

How is urinary buffer action of phosphate affected by acidosis?

Urinary phosphate excretion increases.

What is the primary process of calcium reabsorption in the distal nephron?

Active transport via luminal calcium channels.

What is the role of dietary calcium in bone health?

It contributes to the structure and strength of bones.

What are calcitriol's effects on the intestines?

Enhances calcium and phosphate absorption.

What does high plasma calcium do to the calcium sensing receptor?

It activates and inhibits TALH calcium reabsorption.

How does the kidney respond to increased proximal and TALH sodium reabsorption?

It reduces distal calcium delivery.

What effect does chronic kidney disease have on the ability to handle calcium?

Increased risk of hypercalcemia due to hormonal irregularities.

What happens to calcium levels during hyperparathyroidism?

Calcium levels typically increase.

Why is phosphorus critical for enzymatic reactions?

It's involved in phosphorylation and dephosphorylation.

What are the consequences of calcium and phosphate imbalance in chronic kidney disease?

Can lead to vascular calcifications and bone disorders.

What is the effect of thiazide diuretics beyond increasing sodium excretion?

They reduce urinary calcium concentration.

Why is phosphate regulation important for the kidney?

To prevent phosphate overload and maintain bone health.

What can precipitate calcium out of solution in the urinary tract?

High calcium concentrations leading to stone formation.

What laboratory measurement is indicative of calcium homeostasis?

Total plasma calcium concentration.

Which vitamin is crucial for calcium homeostasis?

Vitamin D.

What effect does renal failure have on calcium metabolism?

It can lead to both elevated calcium and phosphate levels.

What pathway primarily regulates renal calcium reabsorption?

PTH-regulated pathway.

How does the kidney's handling of calcium differ from that of phosphate?

Calcium reabsorption is highly regulated while phosphate has a more passive reabsorption.

What contributes to the formation of calcium phosphate complexes in the body?

Elevated calcium and phosphate levels.

What is the physiological consequence of hypercalcemia?

It can cause hypercalciuria and kidney stones.

What mechanisms are involved in renal phosphate handling?

Filtered and reabsorbed primarily in the proximal tubule.

How does chronic renal failure impact calcium and phosphate management?

It can lead to imbalances that affect bone health and metabolism.

What is the biological significance of phospholipids containing phosphate?

They are essential components of cell membranes.

What is the clinical significance of hyperphosphatemia?

It may indicate renal dysfunction or decreased phosphorus excretion.

What role does sodium play in calcium reabsorption in the kidney?

Sodium reabsorption drives calcium reabsorption.

What does a low phosphate diet aim to achieve in clinical treatments?

To control elevated phosphate levels in kidney disease.

What can high levels of calcium and phosphate complexes lead to in the body?

Calcification in soft tissues and organs.

Which organ plays a vital role in converting vitamin D to its active form?

The kidneys.

What effect does renal tubular acidosis have on phosphate excretion?

It may increase phosphate excretion significantly.

How does calcitonin function in calcium regulation?

It works to lower blood calcium levels.

What condition arises from the imbalance of calcium and phosphate due to renal disease?

Osteodystrophy, affecting bone mineralization.

What is a characteristic of distal tubular calcium reabsorption?

It is active and involves calcium channels.

How is the calcium-sensing receptor significant in regulating calcium levels?

It helps maintain homeostasis by adjusting calcium reabsorption.

What is the primary driver of paracellular calcium reabsorption in the kidney?

Transepithelial potential difference.

Why are calcium and phosphate homeostasis interlinked?

Changes in one can significantly affect the other due to their roles in bone metabolism.

How do diuretics affect calcium concentrations?

By altering sodium and fluid volumes influencing reabsorption.

What renal effect can prolonged high phosphate have?

It hampers calcium reabsorption and contributes to bone loss.

What type of calcium transport mechanism is predominant in the TALH?

Passive paracellular transport.

What can excessive calcium lead to in kidneys quantitatively?

It can precipitate as stones.

What mineral is essential for normal neural function and muscle contraction?

Calcium.

How does dietary fiber affect phosphate absorption?

High fiber intake can reduce phosphate absorption.

What is the role of urinary phosphate in acid-base balance?

It acts as an important buffer.

What treatment options exist for patients with hyperphosphatemia?

Phosphate binders and dietary adjustments.

What condition is observed with low calcitriol levels?

Increased risk of osteomalacia.

How is phosphate reabsorption affected in conditions of overactive parathyroid glands?

Phosphaturia occurs, leading to phosphate wasting.

What inhibits the reabsorption of calcium in the kidneys?

High levels of circulating calcium.

What is the molecular consequence of phosphate in enzymatic processes?

It can activate or deactivate enzymes via phosphorylation.

Which tissues are primarily involved in calcium and phosphate metabolism?

Kidneys, bones, and intestines.

How is calcium involved in coagulation processes?

It acts as a cofactor in clotting cascade reactions.

What dietary considerations are crucial for maintaining healthy phosphate levels?

Balancing intake of phosphorus-rich foods and ensuring adequate calcium.

What illustrations can represent calcium homeostasis?

Bone mineral density and plasma calcium levels.

What can result from poor phosphate regulation in renal failure?

Soft tissue calcifications due to hyperphosphatemia.

How do kidneys primarily manage filtered phosphate?

By reabsorbing it mainly in the proximal tubule.

What triggers the body to absorb calcium through the gut?

Activation of vitamin D into calcitriol.

What are the consequences of impaired renal phosphate excretion?

Potential development of various metabolic pathologies.

What is one of the roles of eggs in dietary phosphate regulation?

They provide a good source of bioavailable phosphate.

What is a common treatment for urinary calcium losses?

Thiazide diuretics.

How do renal and intestinal systems interact for calcium metabolism?

Kidneys activate vitamin D, enhancing gut absorption.

What happens to calcium levels when dietary intake is decreased?

Blood calcium may drop, leading to PTH activation.