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Metabolism > Disorders of Ca Homeostasis In SA & Disorders of the Parathyroid gland > Flashcards

Disorders of Ca Homeostasis In SA & Disorders of the Parathyroid gland Flashcards

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1
Q

Ca distribution within the bone

A
  • 99% in bone (structure, reservoir
  • <1% circulating
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2
Q

Fxns of circulating Ca

A
  • enzyme rxns
  • membrane transport/stability
  • blood coagulation
  • muscle contraction
  • nerve conduction
  • etc.
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3
Q

No. of Parathyroid glands and locations

A

4 - 2 in each thyroid lobe (internal/caudal; external/cranial)

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4
Q

Parathyroid glands play a major role on

A

Ca homeostasis

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5
Q

When can you visually find parathyroid glands?

A

When they are abnormal

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6
Q

Parathyroid hormone action

A
  • bone: rapid release of Ca & PO4
  • kidneys: 1 alpha-hydroxylase feeding into Vit D synthesis; Ca reabsorption, PO4 excretion
  • Intestines: Ca & Phosphorus absorption
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7
Q

Role of calcitonin

A
  • decreases Ca in bone & kidney
  • heterogenous response to HyperCa
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8
Q

Tests of Ca Homeostasis

A
  • Total Ca, Ionised Ca, PO4
  • PTH, PTHrp
  • Vit D
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9
Q

Total Ca testing

A
  • 50% ionised, 50% bound to ALB or complexed
  • does NOT tell about Ca fxn much (only iCa does)
  • prone to error
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10
Q

Ionised Ca testing

A
  • reflects active Ca
  • sensitive to pH: acidosis increases, iCa decreases; Alkalosis decreases; iCa increases?
  • rapid anaerobic analysis: loss of CO2 increases pH; RBC glycolysis decreases pH
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11
Q

How to predice iCa from tCa

A
  • Equations using [ALB]
  • multivariate predictive tools (lab/hospital specific)
    Absence of total hyperCa CANNOT be used to rule out ionised hyperCa
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12
Q

Parathyroid hormones

A
  • rapidly metabolised
  • excreted via kidney
  • sandwich assays
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13
Q

Interpretation of PTH

A
  • high serum iCa & high plasma PTH = primary hyperPTH
  • low serum iCa & high plasma PTH = secondary hyperPTH
  • low serum iCa & low plasma PTH = primary hypoPTH
  • high serum iCa & low plasma PTH = PTH-independent HyperCa (malignancy, Vit D toxicity)
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14
Q

PTHrp

A
  • low concs in adults
  • not good at activating Vit D
  • similar effects as PTH
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15
Q

Vit D form that is PTH-dependent

A

Active 1, 25(OH)2D

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16
Q

Hypercalcaemia effects

A
  • V, anorexia, constipation, risk for pancreatitis
  • listlessness, weakness, stiff gait, shivering
  • Dramatic PU/PD
  • urolithiasis - Ca-excreted stones, UTI - high amounts of bicarbonate
  • kidney injury
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17
Q

Severity of clin signs of hyperCa dependent on…

A
  • magnitude of increase in Ca
  • rate of onset
  • druation
  • underlying disorders
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18
Q

if you see hyperCa in a cat, what should you do next?

A
  • repeat & measure iCa
  • usually non-pathological, so must retest!
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19
Q

Non-pathological causes of hyperCa in cats

A
  • non-fasting
  • physiological (age)
  • lab error
  • hyperlipidaemia
  • spurious
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20
Q

Transient reasons for hyperCa in cats

A

haemoconcentration
hyperproteinaemia
hypothermia - RARE

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21
Q

pathological and persistent causes of hyperCa

A

primary hyperparathyroidism
malignancy-associated
idiopathic, hypoadrenocroticism, kidney failure, granulomatous dz, skeletal lesions, toxins (Vit D, Ca products, raisins/grapes, DMSO)

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22
Q

Finding hyperCa, you must consider…

Study These Flashcards
A

age, protein abnormalities

23
Q

When finding hyperCa, what should you do?

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A
  • repeat or assess iCa
  • assess PO4
  • investigate potential complications
24
Q

Clinical differentials for hypercalcaemia

Study These Flashcards
A

Hyperparathyroidism
Addison’s
Renal dz
Hyperviaminosis D
Idiopathic (cats)
Osteolytic
Neoplastic
Spurious

HARD IONS

25
Rank HyperCa DDx in dogs
1. Neoplasia 2. kidney dz 3. Addison's 4. HyperPTH 5. Hypervitaminosis D - RARE
26
Rank HyperCa DDx in cats
* Neoplasia * kidney dz * idiopathic
27
Malignancy Assoc'd HyperCa
* Humoral HyperCa: PTHrp-related; Lymphoma; predisposes to anal sac adenocarcinoma; other carcinomas * Local osteolytic HyperCa: multiple myeloma (see dots in bones on rads) * v. sick b/c underlying cause
28
Addison's dz hyperCa
* variable effect: iCa +/or tCa in 15-30% cases * disappears w/ txt so due to effects of Addison's on ALB & pH * young, female, pedigree animals * waxing/waning illness * HyperK, HypoNa * Azotaemia
29
Kidney dz hyperCa
* increased tCa (10-20% cats/dogs) * CKD & hyperPO4 * iCa normal or low (<10% high in dogs; more common in cats) * HyperPO4 * Azotaemia
30
Primary hyperparathyroidism hyperCa
* adenoma ~90% - tumour of PTH gland * Older animals: 4-17 yrs old in dogs * Keeshounds, Siamese possibly predisposed
31
Clin Signs of HyperCa in dogs
* often none seen, found incidentally * PU/PD, Urolithiasis/UTI, lethargy/weakness, kidney failure (severe) * marginal increases in tCa; PO4 low * USG: dilute urine from PU/PD (1.012 +/- 0.01)
32
Additional tests for parathyroid masses
* U/S: hypoechoic, 4-10 mm in size; enlarged if found on U/S
33
Hypervitaminosis D causes that can lead to hyperCa
* Iatrogenic due to overdose * Accidental: food, rodenticide, day-blooming jessamine, Calcipotriol (Psoriasis txt) * Granulomatous Dzs: blastomycosis, aspergillosis, angiostrongylosis, panniculitis
34
Idiopathic Hypercalcaemia in cats
* older cats * ? long-haired predisposition - unknown * variable signs; none in 50% * Signs: wt loss, anorexia, V, urolithiasis
35
Testing results of hyperparathyroidism | tCa, iCa, PO4, PTH, PTHrp
high tCa, high iCa normal to low PO4
36
Testing results of kidney dz | tCa, iCa, PO4, PTH, PTHrp
high tCa Normal to high/low iCa high PO4
37
Testing results of Malignancy | tCa, iCa, PO4, PTH, PTHrp
* high tCa, high iCa * Normal to low PO4
38
Testing results of Addison's | tCa, iCa, PO4
high tCa, high/normal/low iCa high PO4
39
Testing for hypervitaminosis D | tCa, iCa, PO4, PTH, PTHrp
high tCa, high iCa, high PO4 low PTH, normal PTHrp
40
Idiopathic testing in cats | tCa, iCa, PO4, PTH, PTHrp
high tCa, high iCa normal to high PO4 low PTH normal PTHrp
41
Txt of hypercalcaemia
* IVF 2x MR, normal saline * Furosemide 2 mg/kg q 8 hr IV or SQ * Zoledronic acid (bisphosphonates) - inhibit bone resorption & do NOT inhibit bone mineralisation via binding to hydroxyapatite crystals
42
Mode of Action of Bisphosphonates used to to treat hypercalcaemia
* inhibits bone resorption * decrease tumour cell viability & prolif * decrease angiogenesis * tumour cell adhesion & invasion * immunomodulatory effect * high efficacy anti-neoplastic therapy * used to decrease pain w/ bone tumours
43
Side Effects of bisphosphonates
* HypoCa * Renal toxicity after repeated high dose IV admin in humans (can be used in kidney P's) * infusion site rxn if leaks into interstitium - MUST BE GIVEN IV * Nausea, anorexia, headache, uveitis * osteonecrosis of jaw after repeated high dose IV use
44
Txt of primary hyperparathyroidism
Bisphosphonates for prolonged txt of bone tumour & Sx unavailable Sx removal HypoCa possible
45
Idiopathic hypercalcaemia in cats
* Diet change: fibre, renal, oxalate * Prednisolone: 5-10 mg/cat/day * Alendronate (bisphosphonate): 10 (5-20) mg wkly
46
HypoCalcaemia
* v. few DDx for clinical HypoCa * Eclampsia, pancreatitis, lack of lactation
47
Spurious causes of HypoCa
Hypoalbuminaemia
48
Marked causes of HypoCa
* Hypoparathyroidism: naturally occuring, post op * eclampsia
49
mod-mild causes of HypoCa
* Pancreatitis * secondary hypoPTH: nutritional * drugs/toxins: ethylene glycol, phosphate, edta, citrate, bicarbonate * kidney dz: acute/chronic, urethral obstruction * intestinal malabsorption: ? HypoMg * metabolic alkalosis * Systemic dz: tumour lysis syndrom, SIRS
50
Clin signs of HypoCa
* intermittent repro, neuromusc signs * neuromuscular irritability * muscle tremors * tetany * seizures (conscious, induced by excitement) * aggression, abd pain due to muscle pain * **facial rubbing from pain * Lenticular cataracts**
51
Dx of HypoCa
* demonstration * signs of other dz * primary hypoparathyroidism -> hyperPO4, low PTH
52
Acute Therapy of HypoCa
* 1-1.5 ml/kg 10% Ca slowly IV over 10-20 mins * 6.5-10 ml/kg 10% Ca gluconate over 24 hrs * **stop if bradycardia dvlps**
53
Chronic txt of HypoCa
* Oral Ca supplementation * Vit D supplementation * Start immediately
54
Monitoring of HypoCa
* regular Ca measurements * try to prevent Hyper Ca - keep w/i ref intervals * stimulus of parathyroid activity if post-op hypoPTH

Metabolism (8 decks)

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