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Musculo-Skeletal > The Skeleton And Metabolism > Flashcards

The Skeleton And Metabolism Flashcards

1
Q

What are the 6 hormones that have skeletal effects?

A

→ Estrogens
→ Androgens

→ Cortisol
→ PTH
→ Vitamin D
→ Calcitonin

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2
Q

What is a hormone secreted from the skeleton?

A

→ FGF-23

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3
Q

How is the calcium distributed in the body?

A

→ most is intracellular
→ the remaining 0.1% is in the plasma

→ half of the 0.1% is free calcium ions
→ the other half is protein bound

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4
Q

What is the only way to increase Ca2+?

A

→ Increase calcium absorption through the gut

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5
Q

What does bone turnover contribute to?

A

→ Homeostasis of serum calcium
→ phosphate

→ and PTH, vit D, calcitonin, FGF-23

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6
Q

What is PTH synthesized from?

A

→ Parathyroid chief cells

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7
Q

What is PTH secreted as?

A

→ 84 AA polypeptide

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8
Q

Where is free Calcium sensed?

A

→ by GPCR on chief cells

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9
Q

What are the endocrine hormones involved in the regulation of bone?

A 
→PTH
→TH
→GH
→IGF
→Oestrogen
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10
Q

How is TH involved in bone regulation?

A

→controls rate at which chondrocytes differentiate into growth plate
→In adults, excess results in activity of osteoclasts

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11
Q

How is GH involved in bone regulation?

A

→regulates osteoclasts differentiation

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12
Q

How is IGF involved in bone regulation?

A

chondrocyte differentiation and linear growth, also osteoblast differentiation

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13
Q

Describe calcitriol synthesis

A

→ 7dehydrocholesterol is in the skin
→ UV light turns it into cholecalcitriol (CCF)

→ 25 hydroxylase adds an OH group in the liver
→ it becomes 25 hydroxyCCG
→ 1a hydroxylase stimulated by PTH in the kidney adds another OH group
→ 1,25 dihydroxyCCF is formed or calcitriol

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14
Q

Where is the regulation site for calcitriol?

A

→ control of 1a hydroxylase in the kidney

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15
Q

What is calcitriol increased by?

A

→ PTH - upregulates 1a hydroxylase

→ Low phosphate

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16
Q

What is the function of calcitriol?

A

→ Increase absorption of Ca and Pi from the GI tract

→ inhibits PTH

17
Q

What are the 4 actions of PTH?

A

→ Promotes release of Ca from bone
→ Increases Ca reabsorption

→ increases renal Pi excretion
→ upregulates 1a hydroxylase activity

18
Q

Describe how PTH works

A

→ hypocalcaemia stimulates PTH
→ PTH binds to osteoblasts and stimulates RANK ligand

→ RANK ligand binds to RANK receptors on osteoclasts
→ Bone breaks down and Ca2+ and phosphate are released into the blood
→

19
Q

What are the effects of PTH release on the kidney?

A

→increased reabsorption of Ca
→increased 1,25-dihydroxy vit D formation
→reduced phosphate reabsorption

20
Q

What are the effects of PTH on the gut?

A

increased calcium absorption via D3

21
Q

What do high Ca and D3 do?

A

D3 inhibit PTH production

22
Q

What is phosphate important for?

A

→for nerve function

23
Q

What does high serum phosphate do?

A

→stimulates FGF23 synthesis in osteocytes

→ to decrease phosphate by increase phosphate excretion in the kidney.

24
Q

What is FG23?

A

→Fibroblast Growth Factor-23

→

25
Q

What are the effects of FG23 on the kidneys and parathyroid?

A

→Decreases phosphate reabsorption in kidneys

→Inhibits PTH production
Decrease release of phosphate via bone resorption

→Inhibits active vitamin D3 production
Decrease phosphate absorption in gut

26
Q

What is Rickets?

A

→Defective mineralisation of normally synthesized bone matrix
→Osteoid are laid down normally but can’t be mineralised into mature bone and remains organic portion of bone

27
Q

What are the two types of Rickets?

A

→Deficiency of vitamin D3 (causing hypocalcemia)

→Deficiency of Phosphate

28
Q

What is oncogenic oesteomalacia?

A

→ mesenchymal tumours producing excess FGF23

Causing excess phosphate excretion

29
Q

What are the outcomes of oesteomalacia?

A

→bonepain/tenderness
fracture
→proximal weakness- upper legs and arms are weak
→bone deformity

30
Q

What are x-ray presentations of oesteomalacia?

A

→Bowing of long bones
→Widening of growth plates
→Looser’s Zones

31
Q

What is looser’s zone?

A

→fracture through one side of bone at 90 degrees to the cortical bone
→ band of bone material of decreased density

32
Q

What are the effects of excess PTH?

A

→Hypercalcemia

→Hypophosphatemia

33
Q

What are primary causes of hyperparathyroidism?

A

→parathyroid adenoma (85-90%)

→chief cell hyperplasia

34
Q

What are the secondary causes of hyperparathyroidism?

A

→chronic renal deficiency

→vit D deficiency

35
Q

What is Osteitis fibrosa cystica?

A

→results from hyperparathyroidism

→bone pain

36
Q

Mnemonic for hyperparathyroidism?

A

Stones (Kidney stones)

Bones (Pain from osteitis fibrosa cystica and excess bone resorption)

Abdominal Moans (acute pancreatitis)

Psychic Groans (psychosis & depression)

37
Q

What are the clinical features of hypercalcaemia?

A

→ Depression, fatigue, anorexia, nausea vomiting
→ Abdominal pain

→ Renal calcification
→ Bone pain

38
Q

How is primary hyperparathyroidism resolved?

A

→ removal of the affected gland

Musculo-Skeletal (6 decks)

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