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COM - Endocrine > Ca And PO4 Metabolism - 2/4 Lopez > Flashcards

Ca And PO4 Metabolism - 2/4 Lopez Flashcards

1
Q

What are the symptoms of hypocalcemia?

A

Hyperreflexia, spontaneous, twitching, m. Cramping, tingling and numbness

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2
Q

What is Chvostek sign?

What does it indicate?

A

Twitching of the facial muscle elicited by tapping on facial nerve

Hypocalcemia

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3
Q

What is Trousseau sign?

What does it indicate?

A

Carpopedal spasm upon inflation of BP cuff

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4
Q

What are the Sx of Hypercalcemia?

A

Dec QT interval, constipation, no appetite, polyuria/dipsia

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5
Q

Low extracellular calcium is equivalent to what?

How does it affect APs?

A

Hypocalcemia

Easier to evoke an AP as it reduces the threshold for Na channels

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6
Q

What happens to the nervous system in Hypercalcemia?

A

Becomes depressed and reflex responses are slowed

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7
Q

If you INC the plasma protein [ ], what happens to total Ca levels?

A

Increase

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8
Q

If [phosphate] increases, what happens to the ionized [Ca]?

A

Decreases

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9
Q

What happens to free ionized calcium in acidemic conditions?

Why?

A

Increased free calcium

Bc less Calcium bound to albumin

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10
Q

What happens to free ionized calcium in alkalemic conditions?

Why?

What can this lead to?

A

Decreased free calcium

Bc more calcium is bound to albumin

Hypocalcemia

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11
Q

How much calcium is ingested every day?

How much is excreted in feces?

Excreted in urine?

A

1000mg

800mg

200mg

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12
Q

What is the distribution of phosphate in the body?

A

85% bone
15 % ICF
1% Plasma

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13
Q

Is Phosphate high inside or outside the cell?

Where does it act as a buffer?

A

Inside

Bone, serum, urine

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14
Q

How is extracellular concentration of phosphate related to Calcium?

A

Inversely

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15
Q

How is PTH synthesized and where?

What is it cleaved to and where does it go?

How is it packaged?

A

PreproPTH on ribosomes

ProPTH to Golgi

Secretory granules

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16
Q

What does PTH do?

What is its stimulus?

A

INC serum Ca levels

DEC plasma Ca levels

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17
Q

What inhibits PTH synthesis and secretion?

A

INC extracellular Ca2+ concentration

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18
Q

What does chronic hypocalcemia do to the parathyroid glands?

A

Causes hyperplasia (secondary hyperparathyroidism)

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19
Q

What do mild decreases in serum [Mg] do?

A

Stimulate PTH secretion

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20
Q

What do severe decreases in serum [Mg] such as in alcoholism cause?

A

Inhibition of PTH synthesis, storage, and secretion

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21
Q

How does PTH act?

What 2nd messenger?

A

GPCR

cAMP

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22
Q

What does Vitamin D do to Ca and Pi plasma concentrations?

A

Increases both

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23
Q

What enzyme in skin synthesizes vitamin D in the skin?

A

7-dehydrocholesterol

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24
Q

How is Vit D stored?

A

As a steroid hormone

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25
Q

What enzyme is responsible for forming the active form of Vitamin D?

Full name of Vitamin D?

A

1alpha-hydroxylase

1,25-dihydroxycholecalciferol

26
Q

What increases the activity of 1alpha-hydroxylase?

A

DEC Ca
DEC phosphate
INC PTH

27
Q

What 2nd messenger does PTH act through to activate transcription of 1alpha-hydroxylase?

What gene does it activate?

A

Gs -> cAMP/PKA

CYP1alpha

28
Q

Where are PTH receptors located?

A

osteoblasts

29
Q

What are the short term actions of PTH?

Long term?

A

Bone formation

INC bone resorption via indirect action on osteoclasts mediated by cytokines

30
Q

How does Vitamin D act? To do what?

A

Synergistically with PTH to stimulate osteoclast activity and bone resorption

31
Q

What is the cell surface protein receptor located on osteoclasts?

What does it bind?

A

RANK

RANKL (primary mediator of osteoclast formation)

32
Q

What is the decoy receptor for RANKL?

What does it do?

What makes it?

A

OPG

Inhibits RANK/RANKL interaction

Osteoblasts

33
Q

What effect does PTH have on RANKL and OPG?

Vitamin D?

A

INC RANKL, DEC OPG

INC RANKL

34
Q

What happens to the cAMP generated in the cells of the PCT of the kidney?

A

Excreted in the urine (urinary cAMP)

35
Q

What is inhibited via phosphorylation in the proximal tubule cells of the kidney once PTH has bound?

What does this cause?

A

Na-Phosphate cotransport

Phosphaturia (INC excretion of Pi in urine)

36
Q

Where is Ca reabsorbed in the kidney after stimulated by PTH?

A

TAL and DCT

37
Q

What does Vitamin D do in the small intestine?

Bone?

A

INC Ca and Pi absorption via calbindin

Sensitized osteoblasts to PTH

38
Q

What does Vitamin D do in the kidney?

Parathyroid gland?

A

Promotes Pi reabsorption by proximal nephron

Directly inhibits PTH gene expression
Directly stimulates CaSR gene expression

39
Q

What is the biologically active form of calcium?

A

Free, ionized Ca2+ (50% of total Ca2+)

40
Q

What does Calcitonin do to Calcium and phosphate?

Where does it act primarily?

A

DEC Ca
DEC PO4

Bone and kidney

41
Q

What effect does a thyroidectomy have on calcitonin and calcium?

A

DEC calcitonin

NO effect on calcium level

42
Q

What effect do thyroid tumors have on calcitonin and calcium metabolism?

A

INC calcitonin

NO effect on Ca

43
Q

What does Estradiol-17Beta stimulate?

What does estrogen promote?

A

Intestinal and renal tubular Ca reabsorption

Survival of osteoblasts -> favoring bone formation

44
Q

What hormone promotes bone resorption and renal Ca wasting and also inhibits intestinal Ca absorption?

A

Adrenal glucocorticoids i.e. Cortisol

45
Q

What is primary hyperparathyroidism commonly caused by?

What is its effect?

A

Parathyroid adenomas

INC excretion of Pi, Ca, cAMP

Will have Hypercalcemia in serum

46
Q

What are the Sx of primary hyperparathyroidism?

Tx?

A

Stone (hypercalciuria)
Bones (INC resorption)
Groans (constipation)

Parathyroidectomy

47
Q 
Does primary hyperparathyroidism have INC/DEC of:
PTH
Ca
Pi
Vit D?
A

INC
INC
DEC
INC

48
Q

Reminder: what are the actions of PTH?

What 2nd messenger does it use?

A

INC serum [Ca]
DEC serum [PO4] -> phosphaturic effect

cAMP -> excreted in ruin for the urinary cAMP effect

49
Q

What are the causes of secondary hyperparathyroidism?

A

Renal failure

Vit D deficiency

50
Q 
Describe the following compared to normal in renal failure:
PTH
Ca
Pi
Vitamin D
A

INC
DEC
INC
DEC

51
Q 
Describe the following compared to normal in Vitamin D deficiency:
PTH
Ca
Pi
Vitamin D
A

INC
DEC
DEC
DEC

52
Q

What are the main causes of hypoparathyroidism?

Symptoms?

A

Thyroid/parathyroid surgery or congenital

Muscle spasm and cramping, seizures, tetany, poor teeth dev, mental deficiency

53
Q 
Describe the following in hypoparathyroidism:
PTH
Ca
Pi
Vitamin D
Urinary excretion
A 
DEC
DEC
INC
DEC
DEC
54
Q

What causes pseudohypoparathyroidism/Albright?

What develops?

A

Defect in Gs for PTH in bone and kidney

Hypocalcemia and hyperphosphatemia

55
Q

Describe the following in Albright osteodystrophy:

PTH
Ca
Pi
Vitamin D

A

INC
DEC
INC
DEC

56
Q

What is the phenotype of Albright?

A

Short stature and neck, obesity, subcutaneous calcification, shortened hand bones

57
Q

What causes humoral Hypercalcemia of malignancy?

How is it different from primary hyperparathyroidism?

A

PTHrP secreted by malignant tumors usually in the breast and lungs

DEC bone formation
DEC PTH levels
DEC Vitamin D

58
Q

Describe the following in humoral Hypercalcemia of malignancy:

PTH
Ca
Pi
Vitamin D

A

DEC
INC
DEC
DEC

59
Q

How do you treat humoral Hypercalcemia of malignancy?

A

Furosemide inhibits renal Ca reabsorption and increases Ca excretion

Etidronate inhibits bone resorption

60
Q

What causes familial hypocalciuria Hypercalcemia (FHH)?

Result?

A

Mutation that inactivates CaSR in parathyroid glands and Ca receptors in TAL of kidney

DEC urinary Ca excretion
INC serum Ca

61
Q

What is pseudo vitamin D-deficient rickets type I characterized by?

Type II?

A

Defective 1alpha-hydroxylase

Defective Vitamin D receptor

62
Q

Tx for Rickets/Osteomalacia?

A

Vit D2 or D3
Ca
Sunlight
1,25-OH2 (calcitriol)

COM - Endocrine (12 decks)

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