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ENDO > calcium > Flashcards

calcium Flashcards

2
Q

• Total body calcium = 1kg (25mol)• __% of this is in bone as hydroxyapatiteo 990g in bone (hydroxyapatite)o __g as non-skeletal calcium

A

9910

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3
Q

Intracellular calcium 0.1 – 1 μmol /LInterstitial fluid calcium 1.5 mmol /LSerum calcium __-__ mmol /L

A

2.2- 2.6

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4
Q

__% bound to serum albumin__% complexed with citrate__% (~1.3 mmol /L) free Ca2+ ions

A

44947

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5
Q

Ca intake: 25mmol__% filtered and reabsorbed so <__% excreted in urine

A

955

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6
Q

in which organ are the following produced?__(caliciol)__(calcidiol)__(calcitriol)

A

Skin Liver Kidney

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7
Q

Renal absorptionProximal tubule and Thick ascending limb: __t/p, not regulated by hormones TAL: transcellular transport: ↑ by_ ↓__Distal tubule: ____transport ↑ by___ and ___ ↓ by ___

A

paracellular PTH, Calcitonintranscellular PTH and calcitriolcalcitonin

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8
Q

OsteoblastsDerived from fibroblast-like precursor cellsSynthesise ___(organic bone matrix)Involved in mineralisation of newly synthesised osteoidBecome surrounded by calcified bone –>

A

osteoid osteocytes

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9
Q

OsteoclastsMultinucleate cells derived from ___Secrete lysosomal enzymes–>resorb bone

A

phagocytes

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10
Q

Osteoblasts are stimulated by: (3)To produce factors that: ↑__differentiation ↑___activity

A

 parathyroid hormone calcitriol (PGE2)osteoclast

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11
Q

Osteoclasts are inactivatedby _____

A

calcitonin

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12
Q

Parathyroid hormoneHypercalcaemic action: ↑ bone resorption by stimulating osteoblasts to produce _________ ↑ renal tubule resorption of calcium ↑ phosphate excretion, lowering serum phosphate–> ↑serum calcium

A

osteoclast activating factors (but calcium excretion may increase because of the greater filtered load due to hypercalcaemia induced by PTH)

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13
Q

Parathyroid hormone via cell surface __: on osteoblasts  on the antiluminal surface of the distal renal tubulesLinked to adenylate cyclase –> cAMP

A

receptors

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14
Q

Parathyroid hormoneContinual secretion, rapid clearance (half-life ~5 min) chief cells have calcium receptor linked to PLC, –>___ and ___ Mg2+ is required for secretion

A

IP3 and DAG hypercalcaemia inhibits secretion hypocalcaemia stimulates secretion

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15
Q

Primary hyperparathyroidism benign tumour of parathyroid glandsSecondary hyperparathyroidism compensation for long-standing____ poor Ca2+ intake / absorption response to low calcitriol in ____

A

hypocalcaemiachronic renal failureSub-periosteal bone resorption may –> cyst formation and bone pain

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16
Q

HypoparathyroidismIatrogenic or Idiopathicsigns (3)Pseudohypoparathyroidism tissue ___to PTH action defect of bone +kidney PTH receptorssigns (3)

A

LOW circulating PTH, hypocalcaemia and hyperphosphataemiaresistance HIGH circulating PTH, hypocalcaemia and hyperphosphataemia

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17
Q

in Hypoparathyroidism, injection of PTH –> ↑__Pseudohypoparathyroidism–> NO increase in__

A

cAMP

18
Q

Hypocalcaemia causes:↑ excitability of nerve tissue paraesthasia, tetany and sometimes __Treatment?

A

epilepsycalcium supplements and calcitriol

19
Q

Calcitonin: the hypocalcaemic hormoneparafollicular ‘C cells’ are embryologically distinct from thyroid cells–> they are derived from ___ ___

A

neural crest

20
Q

CalcitoninActs to lower serum calcium by inhibiting bone demineralisation___stimulates secretion

A

hypercalcaemia

21
Q

medullary thyroid cancer :tumour of the C cells may be assoc w/ tumour of ___cells of the adrenal medulla e.g. MEN II  have very __circulating calcitonin but ___serum calcium

A

chromaffin highnormal

22
Q

Skin: UV light7dehydrocholesterol–>preVitD–>_______

A

calciol (cholecalciferol)

23
Q

calciol-→ calcidiol by what enzyme?where does this reaction occur?

A

25-hydroxylaseliver

24
Q

calcidiol-→ calcitriol by what enzyme?where does this reaction occur?

A

1-hydroxylasekidney

25
Q

Calcitriol induces 24-hydroxylase and represses ____PTH stimulates _________suppresses 1-hydroxylase

A

1-hydroxylase1-hydroxylaseCalcitonin

26
Q

Hypercalcaemic actions of vitamin DStimulation of intestinal calcium absorption rapid action by __________ slow action by induction of calbindin-D Stimulation of reabsorption in distal tubuleStimulation of __to secrete __→___of bone mineral

A

recruitment of calcium transporters to cell surfaceosteoblasts , osteoclast stimulating factorsmobilisation

27
Q

Calcitriol synthesised only in the _____________After admin of radioactive calcitriol, accumulates only in the ______ – the site of its action on calcium reabsorption

A

proximal renal tubuledistal tubule (and collectingduct)

28
Q

nuclear actions of calcitriol circulates bound to Gc globulin binds to ___→ conformational changeactivated VDR forms heterodimer with RXR→ phosphorylation, permits binding of dimer to____

A

vitamin D receptor HRE on DNA

29
Q

interactions between Vit A and D__is required for binding calcitriol, thyroid hormone and PPAR receptors to DNA to act as __________absence of 9-cis-retinoic acid, heterodimers bind to DNA and act as_____

A

RXRtranscriptional activators repressorsFormation of RXR homodimers in high conc 9-cis-retinoic acid downregulates responses to calcitriol, etc as less RXR is available to form active heterodimers

30
Q

other actions of calcitriolInsulin secretion via ___Inhibition of cell proliferation and differentiation viaGPCRs linked to PLCPotentiation of apoptosis induced by vitamin __

A

calbindin induction in beta-cellsAVitamin A deficiency or excess impairs vitamin D function

31
Q

• APUD cells derived from the neural crest, are those that develop to form:

A

o C-cells of the thyroid glando Chromaffin cells of the adrenal medulla

32
Q

• APUD cells that are NOT derived from the neural crest are found in the

A

o Islet of Langerhanso Anterior pituitary gland o Gastro-intestinal glands

33
Q

• Defects in neural crest-derived APUD cells →__• Defects in APUD cells not derived from the neural crest → __.

A

MEN2MEN1

34
Q

The secretion of the PTH protein requires magnesium; deficiency can impair PTH secretion in premature→___. • Of the aa in PTH, only __residues at the N-terminus required for full activity.

A

hypocalcaemia34

35
Q

• Gene encoding calcitonin- subject to ___splicing.• In C-cells: first 4 exons translated →an N-terminal protein + calcitonin. • In the brain: 4th exon skipped→ “calcitonin gene-related peptide” (CGRP). a potent __,may also act as neurotransmitter.

A

alternative vasodilator

36
Q

symptoms of hypercalcaemia?

A

• Formation of renal calculi (kidney stones) in calyces• calcium-phosphate complexes may move down ureter:→ o Haematuria o Recurrent renal tract infections (pyelonephritis)↑ PTH/calcitriol ↑ subperiosteal bone reabsorption  cyst formation & bone pain.

37
Q

Why is hypercalcaemia common feature of malignant disease?

A

when malignant cells metastasise to bone, they secrete “OAFs” (PGs and interleukins) stimulating bone resorption, ↓serum calcium Common feature of cancerous cells (incl unmetastasised cells) : synthesis of parathyroid hormone related peptide (PTHRP): a hypercalcaemic hormone

38
Q

symptoms of hypocalcaemia?

A

o Tetanyo Myopathyo “Pins & needles” (paraesthesia)o extreme cases, epilepsy (due to↑ excitability of neurones)skeletal malformities

ENDO (23 decks)

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