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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
What enzyme is responsible for forming the active form of Vitamin D? Full name of Vitamin D?
1alpha-hydroxylase 1,25-dihydroxycholecalciferol
26
What increases the activity of 1alpha-hydroxylase?
DEC Ca DEC phosphate INC PTH
27
What 2nd messenger does PTH act through to activate transcription of 1alpha-hydroxylase? What gene does it activate?
Gs -> cAMP/PKA CYP1alpha
28
Where are PTH receptors located?
osteoblasts
29
What are the short term actions of PTH? Long term?
Bone formation INC bone resorption via indirect action on osteoclasts mediated by cytokines
30
How does Vitamin D act? To do what?
Synergistically with PTH to stimulate osteoclast activity and bone resorption
31
What is the cell surface protein receptor located on osteoclasts? What does it bind?
RANK RANKL (primary mediator of osteoclast formation)
32
What is the decoy receptor for RANKL? What does it do? What makes it?
OPG Inhibits RANK/RANKL interaction Osteoblasts
33
What effect does PTH have on RANKL and OPG? Vitamin D?
INC RANKL, DEC OPG INC RANKL
34
What happens to the cAMP generated in the cells of the PCT of the kidney?
Excreted in the urine (urinary cAMP)
35
What is inhibited via phosphorylation in the proximal tubule cells of the kidney once PTH has bound? What does this cause?
Na-Phosphate cotransport Phosphaturia (INC excretion of Pi in urine)
36
Where is Ca reabsorbed in the kidney after stimulated by PTH?
TAL and DCT
37
What does Vitamin D do in the small intestine? Bone?
INC Ca and Pi absorption via calbindin Sensitized osteoblasts to PTH
38
What does Vitamin D do in the kidney? Parathyroid gland?
Promotes Pi reabsorption by proximal nephron Directly inhibits PTH gene expression Directly stimulates CaSR gene expression
39
What is the biologically active form of calcium?
Free, ionized Ca2+ (50% of total Ca2+)
40
What does Calcitonin do to Calcium and phosphate? Where does it act primarily?
DEC Ca DEC PO4 Bone and kidney
41
What effect does a thyroidectomy have on calcitonin and calcium?
DEC calcitonin NO effect on calcium level
42
What effect do thyroid tumors have on calcitonin and calcium metabolism?
INC calcitonin NO effect on Ca
43
What does Estradiol-17Beta stimulate? What does estrogen promote?
Intestinal and renal tubular Ca reabsorption Survival of osteoblasts -> favoring bone formation
44
What hormone promotes bone resorption and renal Ca wasting and also inhibits intestinal Ca absorption?
Adrenal glucocorticoids i.e. Cortisol
45
What is primary hyperparathyroidism commonly caused by? What is its effect?
Parathyroid adenomas INC excretion of Pi, Ca, cAMP Will have Hypercalcemia in serum
46
What are the Sx of primary hyperparathyroidism? Tx?
Stone (hypercalciuria) Bones (INC resorption) Groans (constipation) Parathyroidectomy
47
``` Does primary hyperparathyroidism have INC/DEC of: PTH Ca Pi Vit D? ```
INC INC DEC INC
48
Reminder: what are the actions of PTH? What 2nd messenger does it use?
INC serum [Ca] DEC serum [PO4] -> phosphaturic effect cAMP -> excreted in ruin for the urinary cAMP effect
49
What are the causes of secondary hyperparathyroidism?
Renal failure | Vit D deficiency
50
``` Describe the following compared to normal in renal failure: PTH Ca Pi Vitamin D ```
INC DEC INC DEC
51
``` Describe the following compared to normal in Vitamin D deficiency: PTH Ca Pi Vitamin D ```
INC DEC DEC DEC
52
What are the main causes of hypoparathyroidism? Symptoms?
Thyroid/parathyroid surgery or congenital Muscle spasm and cramping, seizures, tetany, poor teeth dev, mental deficiency
53
``` Describe the following in hypoparathyroidism: PTH Ca Pi Vitamin D Urinary excretion ```
``` DEC DEC INC DEC DEC ```
54
What causes pseudohypoparathyroidism/Albright? What develops?
Defect in Gs for PTH in bone and kidney Hypocalcemia and hyperphosphatemia
55
Describe the following in Albright osteodystrophy: PTH Ca Pi Vitamin D
INC DEC INC DEC
56
What is the phenotype of Albright?
Short stature and neck, obesity, subcutaneous calcification, shortened hand bones
57
What causes humoral Hypercalcemia of malignancy? How is it different from primary hyperparathyroidism?
PTHrP secreted by malignant tumors usually in the breast and lungs DEC bone formation DEC PTH levels DEC Vitamin D
58
Describe the following in humoral Hypercalcemia of malignancy: PTH Ca Pi Vitamin D
DEC INC DEC DEC
59
How do you treat humoral Hypercalcemia of malignancy?
Furosemide inhibits renal Ca reabsorption and increases Ca excretion Etidronate inhibits bone resorption
60
What causes familial hypocalciuria Hypercalcemia (FHH)? Result?
Mutation that inactivates CaSR in parathyroid glands and Ca receptors in TAL of kidney DEC urinary Ca excretion INC serum Ca
61
What is pseudo vitamin D-deficient rickets type I characterized by? Type II?
Defective 1alpha-hydroxylase Defective Vitamin D receptor
62
Tx for Rickets/Osteomalacia?
Vit D2 or D3 Ca Sunlight 1,25-OH2 (calcitriol)

COM - Endocrine (12 decks)

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