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BRS 1b > Calcium Dysregulation > Flashcards

Calcium Dysregulation Flashcards

1
Q

Which hormones increase serum calcium?

A

Vitamin D

Parathyroid hormone

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2
Q

Which hormone decreases serum calcium?

A

Calcitonin

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3
Q

What is the precursor molecule of pre-vitamin d3?

A

7-dehydrocholesterol

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4
Q

Which enzyme catalyses the conversion of vitamin d3 to 25-hydroxycholecalciferol?

A

Renal 25-hydroxylase

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5
Q

Which enzyme catalyses the conversion of 25-hydroxycholecaliciferol?

A

1-alpha hydroxylase

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6
Q

What are the effects of calcitriol?

A

Increased osteoblast activity
Increased enterocyte calcium absorption (Calbindin-D expression)
Increased serum phosphate absorption
Increased calcium and phosphate reabsorption

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7
Q

What are the effects of PTH?

A 
Increased calcium resorption from bone
Increased calcium absorption
Increased phosphate absorption 
Increased calcium reabsorption 
Increased phosphate excretion 
Increased 1-alpha-hydroxylase activity
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8
Q

Which transporter is responsible for phosphate renal reabsorption?

A

NPT2

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9
Q

What effects does PTH have on renal phosphate reabsorption?

A

Inhibits NPT2 transporter, therefore in hyperparathyroidism , serum phosphate is low due to increased urine phosphate excretion

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10
Q

What effect does FGF-23 have on calcitriol?

A

Inhibits the synthesis of calcitriol.

Less phosphate reabsorption from gut

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11
Q

What are the clinical features of hypocalcaemia?

A

Sensitises excitable tissues, muscle cramps, tetany, tingling

Paraesthesia (hands, mouth, feet, lips)

Convulsions

Arrhythmias

Tetany

CATs go numb

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12
Q

Which sign is attributed to twitching of the zygomatic arch in patients with hypocalcaemia?

A

Chvostek’s sign

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13
Q

What is trousseau’s sign in hypocalcaemia?

A

Carpopedal spasm

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14
Q

What are the causes of hypocalcaemia?

A

Low PTH levels = hypoparathyroidism

  • Surgical- neck surgery
  • Auto-immune
  • Magnesium deficiency
  • Congenital

Low vitamin D levels
-Deficiency

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15
Q

What are the signs of hypercalcaemia?

A

Stones- renal effects- nephrocalcinosis (kidney stones and renal colic)

Abdominal moans- GI effects (Anorexia, nausea, dyspepsia, constipation and pancreatitis)

Psychic groans - Fatigue, depression, impaired concentration, altered mentation, coma

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16
Q

What are the causes of hypercalcaemia?

A

Primary hyperparathyroidism

  • Excess production of PTH (parathyroid gland adenoma)
  • There is no negative feeadback (elevated production of PTH)

Malignancy (bony metastases, produce local factors to activate osteoclast)

Certain cancer (squamous cell carcinoma), secrete PTH related peptide that acts at PTH receptors

17
Q

Which cells detect serum calcium in parathyroid gland?

A

G-coupled calcium sensing receptors on the parathyroid cells.

18
Q

What is the relationship between PTH and calcium ions?

A

There is an inverse relationship between calcium concentration and PTH production

19
Q

What is the main cause of primary hyperparathyroidism?

A

Parathyroid adenoma –> Elevated production of PTH

Calcium increases, however there is no negative feedback to PTH

20
Q

What is the biochemistry of hyperparathyroidism?

A

High calcium
Low phosphate - increased renal phosphate excretion (inhibition of NPT2)
High PTH

21
Q

What is the main treatment of primary hyperparathyroidism?

A

Parathyroidectomy

22
Q

What are the associated risks of untreated hyperparathyroidism?

A

Osteoporosis
Renal caliculi
Mental function and mood is impaired.

23
Q

What is serum calcium of secondary hyperparathyroidism?

A

Low serum calcium, physiological response to hypocalcaemia

24
Q

What are the common causes of secondary hyperparatyroidism?

A

Vitamin D deficiency

25
Q

What is the treatment of secondary hyperparathyroidism?

A

Vitamin D replacement

25-hydroxy vitamin D

26
Q

What is the treatment for secondary hyperparathyroidism in patients with renal failure?

A

Alfacalcidol (inadequate 1-alpha hydroxylation)

27
Q

What is the common cause of tertiary hyperparathyroidism?

A

Chronic renal failure

Parathyroid gland hyperplasia- autonomous PTH secretion causes hypercalcaemia.

28
Q

What is the normal physiological response to hypercalcaemia for PTH?

A

PTH decreases (suppressed)

29
Q

What is the surrogate marker to measure inactive Vitamin-D?

A

25-Hydroxy vitamin D.

BRS 1b (62 decks)

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