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Endocrine > Regualtion Of Calcium And Phosphate > Flashcards

Regualtion Of Calcium And Phosphate Flashcards

1
Q

What are the signs of hypercalcemia?

A

Decreased QT interval, hyporeflexia, polyuria, poludipsia

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2
Q

What does hypocalcemia do to the membrane potential?

A

Reduces activation threshold of Na+ channels. These are Ca+ dependent Na+ channels. Ca2+ normally inhibits them.

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3
Q

What does hypercalcemia due to the membrane potential?

A

Increase activation threshold (more negative), makes it harder to elicit an action potential

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4
Q

What does academia do to free ionized calcium levels?

A

Increases free ionized calcium concentration due to less Ca2+ bound to albumin

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5
Q

What does alkalemia due to free ionized Ca2+ levels?

A

Decrease free ionized Ca2+.

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6
Q

What three hormones regulate Ca2+?

A

PTH, Calcitonin, Vit. D,

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7
Q

What is the relationship between Phosphate and Calcium concentrations?

A

Inverse.

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8
Q

Increase in extracellular Ca2+ concentration inhibits PTH release via what molecular sensor?

A

CaSR. Inhibits PTH gene expression and PTH exocytosis.

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9
Q

What are the actions of PTH?

A

Increase serum calcium and decrease serum phosphate.

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10
Q

What are the actions of PTH on bone, kidney, and intestine?

A

Bone-> incrase resorption
Kidney-> decrease phosphate reabsorption, increase Ca2+ reabsorption, increase urinary cAMP
Intestine-> increase Ca2+ absorption via Vit D.

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11
Q

What is the second messenger for PTH?

A

CAMP

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12
Q

PTH stimulates what gene expression in response to low calcium concentration?

A

CYP1-alpha. This increases the activity of 1 alpha-hydroxylase.

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13
Q

what cell type of bone are PTH receptors located on?

A

Osteoblasts

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14
Q

What are the short term and long term actions of PTH on bone?

A

Short term-> bone formation via direct action on osteoblast.

Long term-> increase bone resorption via indirect action of osteoclasts mediated by cytokines released from osteoblasts.

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15
Q

Vit D and PTH both have what effect on bone?

A

Bone resorption.

  • but Vit D increases phosphate reabsorption and PTH decreases it*
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16
Q

What is the primary mediator of osteoclast formation?

A

RANKL ( receptor activator for NF-kappaB ligand)

17
Q

What is Osteoprotegrin?

A

Soluble protein produced by osteoblasts, decoy receptor for RANKL. Inhibits RANKL/RANK interaction.

18
Q

What is the mechanism of action of PTH on the proximal tubule in relation to phosphate?

A

Decrease uptake by inhibiting the Na+/phosphate cotransporter on the basolateral membrane. This will also cause the increase in cAMP in the urine.

19
Q

What are the actions of Vit D on the kidney?

A

Ca2+ and phosphate reabsorption

20
Q

What is the mechanism of action of Vit D on the intestine for Calcium reabsorption?

A
  • Increase phosphate reabsorption via the Na/ phosphate cotransporter (luminal side).
  • Increase Na/ Ca antiporter on the basolateral side.
  • Also incrase active transport of Ca on basolateral side.

-Actions are is Calbindin protein

21
Q

Where does PTH stimulate Ca2+ reabsoprtion in the kidney?

A

Distal Tubule.

22
Q

What are the actions of calcitonin on bone and kidney?

A
  • inhibits bone resorption thus decreasing Ca2+ and phosphate levels.
  • major stimulus for release in increased serum Ca2+.
23
Q

What is the effect of estradiol -17beta on Ca2+ and phosphate in the blood?

A

-stimulates intestinal Ca2+ absorption and renal tubular Ca2+ reabsorption.

24
Q

What is estrogens effect on osteoblasts and osteoclasts?

A

-Stimulates osteoblasts survival and osteoclast apoptosis

25
Q

What are the effects of adrenal glucocorticoids on Ca2+ regulation?

A

-Promote bone resorption and renal Ca2+ wasting. Also inhibit intestinal Ca2+ absorption.

26
Q

What are the findings for PTH, Ca2+, Pi, and Vit D levels for Primary hyperparathyroidism?

A 
PTH- high
Ca2+- high
Pi- low
Vit D- high
-also increased bone resorption.
27
Q

What are the levels of PTH, Ca2+, Pi, and Vit D for Secondary hyperparathyroidism (Renal cause and Vit D deficiency)?

A 
Renal:
PTH- high
Ca2+- low ( due to Ca2+ completing with phospahte)
Pi- high 
Vit D- low
Vit D deficiency:
PTH-high
Ca2+- low
Pi- low
Vit D- low
28
Q

What are the levels of PTH, Ca2+, Pi, Vit D in Hypoparathyroidism?

A

PTH- low
Ca2+- low
Pi- high
Vit D- low

29
Q

What is the etiology of Albright hereditary osteodystropy?

A

-Inherited autosomal dominant disorder, Gs for PTH in bone and kidney is defective.

30
Q

What are the levels of PTH, Ca2+, Pi, Vit D in Albright hereditary osteodystropy?

A

PTH- high
Ca2+- low
Pi- high
Vit D- low

31
Q

What is the etiology of Humoral hypercalcemia of malignancy?

A

PTH-related peptide,produced by a tumor, can bind to the same receptor as PTH and stimulate it.

32
Q

What are the levels of PTH, Ca2+, Pi, and Vit D in humoral hypercalcemia of malignancy?

A

PTH- low
Ca2+- high
Pi- low
Vit D- low

33
Q

What is the etiology of familial hypocalcuiric hypercalcemia?

A

Autosomal dominant disorder. Mutation that inactivates CaSR and leads to increased release of PTH

34
Q

What are the levels of serum Ca2+, urine Ca2+, in familial hypocalcuiric hypercalcemia?

A

Serum calcium- increased

Urine calcium- decreased

35
Q

What is the cause of Rickets?

A
  • Insufficient amount of Ca2+ and Pi are available to mineralize growing bone.
  • Characterized by growth failure and skeletal deformities
36
Q

What is osteomalacia?

A

New bone fails to mineralize. Characterized by bending and softening of weight-bearing bones.

37
Q

What is the deficiency in vitamin D-dependent rickets type 1?

A

1 alpha- hydroxylase

38
Q

What is the deficiency in vitamin D-dependent rickets type 2?

A

Vitamin D receptor.

39
Q

What are the symptoms of hypocalcemia?

A
  • Hyperflexia, spontaneous twitching, tingling, numbness.

- positive Chvostek sign and trousseau sign

Endocrine (15 decks)

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