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Neuroendocrine > Calcium and Phosphate Homeostasis > Flashcards

Calcium and Phosphate Homeostasis Flashcards

1
Q

Where is most of the body’s Calcium found?

A

Bones and teeth

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2
Q

What is the biologically active form of Calcium?

A

Free, ionized

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3
Q

Decreased calcium levels in the plasma

A

Hypocalcemia

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4
Q

Increased calcium levels in the plasma

A

Hypercalcemia

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5
Q

What are some signs of hypocalcemia?

A

Muscle twitching, hyperreflexia, muscle cramps and tingling and numbness

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6
Q

What does hypocalcemia do to the membrane excitability?

A

It increases membrane excitability (spontaneous APs) by reducing the activation threshold of sodium channels

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7
Q

What are 3 things that can change the calcium concentration in the plasma?

A

Changes in plasma protein concentration
Changes in anion concentration
Acid-base abnormalities

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8
Q

If there is an increase in plasma protein, what does that do to the calcium concentration?

A

Increases total Calcium

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9
Q

If there is an increase in an anion (ex. phosphate), what does that do to the calcium concentration?

A

Decreases ionized Calcium

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10
Q

Alters ionized concentration of calcium by changing fraction of calcium bound to albumin

A

Acid-base abnormalities

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11
Q

If less calcium is bound to albumin, what does that do to ionized calcium levels in the plasma?

A

Increases them (acidemia)

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12
Q

If more calcium is bound to albumin, what does that do to ionized calcium levels in the plasma?

A

Decreases them (Alkalemia)

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13
Q

What are the 3 main hormones that control calcium and phosphate homeostasis?

A

PTH, Vitamin D and Calcitonin

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14
Q

In order to maintain calcium balance, what must the kidney do?

A

Excrete the same amount of calcium that the GI tract absorbed

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15
Q

What is the optimal level of calcium in the ECF?

A

10 mg/ml

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16
Q

Phosphate concentration is _____ related to calcium concentrations

A

Inversely

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17
Q

Only 50% of calcium is ionized, what is the percentage of phosphate that is ionized?

A

84%

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18
Q

What cells in the parathyroid synthesize and secrete PTH?

A

Chief cells

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19
Q

If there is LOW calcium plasma levels, what will be secreted MORE?

A

PTH

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20
Q

What inhibits PTH synthesis and secretion?

A

Hypercalcemia

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21
Q

What senses calcium plasma levels?

A

CaSR receptors

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22
Q

If there is low calcium, PTH will increase. What are its main actions?

A

Increase bone resorption
Increase Calcium reabsorption from kidneys
Increase Calcium reabsorption from intestines

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23
Q

What type of hormone is Vitamin D?

A

Steroid hormone

24
Q

What is the action of Vitamin D on calcium and phosphate concentrations?

A

INCREASE

25
Q

How does Vitamin D promote bone mineralization?

A

Increases CaXPi

26
Q

What activates 1alpha-hydroxylase to form the active version of Vitamin D?

A

Low calcium and low phosphate

High PTH

27
Q

Where is Vitamin D synthesis?

A

Kidney tubule

28
Q

What activates CYP1alpha gene?

A

Increased PTH

29
Q

What suppresses the CYP1alpha gene using what mechanism?

A

Increased calcium suppresses it using CaSR

30
Q

The CYP1alpha gene codes for what?

A

1alpha-hydroxylase which activates Vitamin D

31
Q

Short term, what does PTH do to bone?

A

Bone formation

32
Q

Long term, what does PTH do to bone?

A

Bone resorption (degradation)

33
Q

What helps PTH synergistically stimulate osteoclast activity for bone resorption?

A

Vitamin D

34
Q

HOW does PTH increase bone resorption?

A

Increases RANKL release from osteoblasts and decreases OPG

35
Q

HOW does Vitamin D increase bone resorption?

A

Increases RANKL

36
Q

Osteoblasts release RankL, how does that result in bone resorption?

A

It binds RANK receptors on osteoclasts and activates them

37
Q

Where are PTH receptors located for bone remodeling?

A

On osteoBlasts

38
Q

What activates the thyroid gland to release calcitonin?

A

Increased Calcium levels

39
Q

What does Calcitonin do?

A

Stimulates bone formation and decreases the reuptake of calcium in the kidney

40
Q

For bone formation, where are calcitonin receptors?

A

On osteoClasts to reduce their activity

41
Q

Increased PTH which results in increased Ca

- stones, bones and groans

A

Primary hyperparathyroidism

42
Q

Primary hyperparathyroidism

A

Increased PTH, Ca, Vitamin D

Decreased Pi

43
Q

Decreased Ca which causes an increased PTH

A

Secondary hyperparathyroidism

44
Q

Secondary hyperparathyroidism

A

Increased PTH

Decreased Ca, Vitamin D

45
Q

Decreased PTH which causes decreased calcium

A

Hypoparathyroidism

46
Q

Hypoparathyroidism

A

Decreased PTH, Ca, Vitamin D

Increased Pi

47
Q

Autosomal dominant disorder that causes PTH resistance

- short, short neck, obese, short fingers

A

Albright hereditary osteodystrophy

48
Q

Albright hereditary osteodystropy

A

Increased PTH, Pi

Decreased Ca, Vitamin D

49
Q

Tumors that produce PTHrP that will bind the same receptor as PTH

A

Humerol hypercalcemia of malignancy

50
Q

Humerol hypercalcemia of malignancy

A

Increased PTHrP, Ca

Decreased PTH, Pi, vitamin D

51
Q

Autosomal dominant disorder that causes mutations in CaSR in the parathyroid glands and kidney

A

Familial hypocalciuric hypercalcemia (FHH)

52
Q

Familial hypocalciuric hypercalcemia

A

Increased serum calcium

Decreased urine calcium

53
Q

Vitamin D deficiency disorders?

A

Rickets and Osteomalacia

54
Q

Growth failure and skeletal deformities in children

A

Rickets - vitamin D deficiency

55
Q

Bone tenderness, fracture, bending and softening in adults

A

Osteomalacia

56
Q

Type 1 rickets is due to?

A

Decreased 1alpha-hydroxylase

Neuroendocrine (47 decks)

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