7. Regulation of calcium and phosphate Flashcards

Question

How does PTH affect kidney?

Answer 1

* increased calcium reabsorption in distal tubules so plasma calcium conc increases and decreased urinary excretion of calcium * decreased phosphate reabsorption in proximal tubule so plasma phosphate conc decreases and increased excretion * increased active vitamin d formation --> increased calcium absorption in intestines --> increased plasma calcium conc

Answer 2

``` CKD Hypoparathyroidism Rickets & osteomalacia Tissue injury Alkalosis ```

Answer 3

Causes hyperphosphatemia, thus Ca levels fall | Also low levels of activated vitamin D, so less Ca absorpted in the gut

Answer 4

Release of intracellular phosphate, causing Ca levels to fall

Answer 5

Reduced H+ available to bind to protein, so more Ca2+ binds | Even though the total Ca remains same, there is decreased Ca2+ so there is less for cellular processes

Answer 6

Oral/IV Ca | Alfacalcidol - vitamin D analogue

Answer 7

Decreased Ca2+ results in neuromuscular excitability leading to tetany with convulsions, hand and feet muscle cramps and cardiac arrythmias

Answer 8

``` • Hypercalcemia makes cells less excitable resulting in slow reflexes, muscle weakness and constipation • Symptoms and signs of hypercalcemia are: • Polyuria • Polydipsia • ‘Bones’ (bone pain and fractures • ‘Stones’ (renal calculi) • ‘Groans’ (abdominal pain, vomiting and constipation) • ‘Moans’ (depression or confusion) ```

Answer 9

• Primary hyperparathyroidism • Sudden acidosis, resulting in the release of bound calcium, which becomes ionized Ca2+ • Increased intestinal absorption due to excess vitamin D or ingestion of calcium • Bone destruction resulting in increased Ca2+ release from bone – usually caused by secondary deposits from malignancy or myeloma • Granulomatous disease • Drugs e.g. thiazides • Tertiary hyperparathyroidism in CKD • Hypermagnesem

Answer 10

Treatment is of the underlying cause, with fluids for rehydration and bisphosphonates

Answer 11

• Hypophosphatemia is caused by an excessive loss of PO4 3- • Causes include: • Hyperparathyroidism • Reduced absorption from GI (alcohol and medications such as antacids) • Significantly reduced intake - Malnourished - Anorexia nervosa • Refeeding syndrome - shift of phosphate from blood to cells when start to eat • Diabetic ketoacidosis – insulin given • Respiratory alkalosis

Answer 12

Decreased CO2 Intracellular CO2 diffuses out pH in the cell increases, which stimulates glycolysis Glycolysis uses up phosphate

Answer 13

* ‘Stones’ – kidney and gallbladder * ‘Thrones’ - polyuria * ‘Bones’ – pain * ‘Groans’ – constipation and muscle weakness * ‘Psychiatric overtones’ – depressed mood and confusion

Answer 14

involves oral or intravenous phosphate and close monitoring of blood levels • In severe malnutrition it is important to increase caloric intake gradually to avoid refeeding syndrome

Answer 15

* Chronic kidney disease (↓GFR) * Secondary hyperparathyroidism (kidneys unable to reabsorb Ca2+) * Pseudohypoparathyroidism * Hypoparathyroidism * Excessive intake (diet or phosphate based laxities) * Cell death (crush syndrome, tumor lysis, rhabdomyolysis) * Respiratory acidosis * Diabetic ketoacidosis

Answer 16

[CO2] very high, so it diffuses into cells Reacts with water to become carbonic acid Carbonic acid breaks down into H+ and HCO3- This lowers the pH inside the cell, which inhibits glycolysis Hence, less P used up

Answer 17

Crushing injury to skeletal muscle which leads to major shock and kidney failure AKA traumatic Rhabdomyolysis

Answer 18

* No symptoms with mild hyperphosphatemia * Signs and symptoms of severe hyperphosphatemia include: * Spontaneous firing of neurons * Tetany * Involuntary contraction of muscles * Calcium phosphate crystal formation – kidney stones

Answer 19

Reduced dietary intake Phosphate binders Forced diuresis using loop diuretics to reduce reabsorption in the PCT

Answer 20

Genetic defect where the kidney is unresponsive to PTH

Answer 21

Low insulin | So P not removed from the blood