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MSS > The skeleton and metabolism > Flashcards

The skeleton and metabolism Flashcards

1
Q

What hormones cause a skeletal effect?

A

-Oestrogen
-Androgens
-Cortisol
-PTH
-Vitamin D
Calcitonin

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2
Q

What hormone is secreted from the skeleton?

A

FGF-23

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3
Q

What does bone serve homeostasis of?

A

Bone turnover serves homeostasis of serum calcium, phosphate in conjunction with:

  • PTH
  • Vitamin D
  • Calcitonin
  • FGF-23
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4
Q

Where is the parathyroid gland located?

A

Located behind thyroid gland

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5
Q

What is PTH synthesised by?

A

Synthesised by parathyroid chief cells

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6
Q

What’s the life of PTH in circulation like?

A

Short half life in circulaiton

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7
Q

What is PTH secreted as?

A

Secreted as an 84 amino acid polypeptide

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8
Q

What is PTH’s major role?

A

Major role in defence against hypocalcaemia

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9
Q

What is free Ca sensed by?

A

Free Ca sensed by GPCR on chief cells

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10
Q

What happens when Ca binds with GPCR on chief cells?

A

Ca binding to GPCR on chief cells suppresses PTH release

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11
Q

What is calcitriol actually?

A

Calcitriol is actually a steroid hormone, not a vitamin

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12
Q

Where is calcitriol synthesised and in response to what/

A

Synthesised in skin in response to exposure to UV

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13
Q

What are the 2 steps which form the active hormone, calcitriol?

A

Activated by 2 steps:

  1. 25 hydroxylation in liver to form 25OH D3 the major circulatory metabolite
  2. 1alpha hydroxylation of 25OH D3 in kidney produces 1,25(OH)2D3, or calcitriol, the active hormone
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14
Q

What is the site of regulation of calcitriol?

A

Site of regulation is control of 1alpha hydroxylase in kidney

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15
Q

What is calcitriol increased by?

A

Increased by:

  • PTH
  • Low phosphate
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16
Q

What are the actions of calcitriol?

A

-To increase absorption of Ca and Pi from GI tract
-Inhibits PTH secretion and transcription
Complex effects on bone, generally in synergy with PTH

17
Q

What are the actions of PTH?

A
  • Promotes release of Ca from bone
  • Increases renal Ca reabsorption
  • Increases renal Pi excretion
  • Upregulates 1alpha hydroxylase activity
18
Q

What are the actions of PTH on bone?

A
  • PTH receptors on osteoblasts and osteocytes
  • Promotes bone formation
  • Activates osteoclasts via RANK-L
19
Q

What does the effect of PTH depend on?

A

Effect depends on concentration dynamics:

  • Intermittent low doses are anabolic
  • Persistent high concentration leads to excess resorption over formation-bone loss
20
Q

How many amino acid long is calcitonin?

A

32 amino acids long peptide

21
Q

What is calcitonin secreted by>

A

Secreted by C cells of thyroid

22
Q

What is the stimulus for secretion of calcitonin?

A

Stimulus for secretion is high [Ca2+]

23
Q

What does calcitonin do in kidneys?

A

Decreases calcium and phosphate reabsorption

24
Q

What does calcitonin do in bone?

A

Decreases bone resorption by inhibiting osteoclast activity

25
Q

What is synthetic calcitonin used for?

A

Synthetic calcitonin is used in the treatment of paget’s disease of bone and severe osteoporosis

26
Q

What is FGF-23?

A

A hormone secreted by osteocytes

27
Q

What is the central role of FGF-23?

A

Central role is in phosphate homeostasis

28
Q

What are the actions of FGF-23?

A
  • Increased by calcitriol and Pi
  • Inhibits calcitriol synthesis
  • Increases renal Pi excretion
29
Q

What is hypophosphatemic rickets?

A

Rare phosphate wasting condition leading to bone mineralization defects

30
Q

What is the normal range of calcium>

A

2.2-2.6mM

31
Q

What are the clinical features of hypercalcemia?

A
  • Depression, fatigue, anorexia, nausea, vomitting
  • Abdominal pain
  • Kidney stones
  • Bone pain
32
Q

What are the causes of hypercalcemia in ambulatory patients ?

A

Causes are primary hyperparathyroidism

33
Q

What are the causes of hypercalcemia in hospitalised patients?

A

Causes are Malignancy

34
Q

What are less common causes of hypercalcemia?

A
  • Hyperthyroidism

- Excessive intake of vitamin D

35
Q

What is primary hyperparathyroidism usually due to?

A

Usually due to benign adenoma in one or more PT glands

36
Q

How is primary hyperparathyroidism resolved?

A

Resolved by surgical removal

MSS (5 decks)

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