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How is serum PTH level controlled?
PTH is constantly produced and stored in secretory vesicles; the amount secreted and degraded controls serum level
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Low ________ stimulates PTH release; _____ also to a lesser extent.
iCa2+; Mg2+
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PTH stimulates _________ from the kidney, a negative regulator, and _________.
calcitriol; active Vit D
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On histopath, more cytoplasm in PTG chief cells means _________; this can be caused by _________.
more PTH production; chronic hypocalcemia
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How does acute hypercalcemia affect the PTG?
secretory granules accumulate and are degraded
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How does chronic hypercalcemia affect the PTG?
chief cells atrophy, decreased number of cells
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Causes of primary hypoparathyroidism. (2)
[primary is rare] immune-mediated lymphocytic parathyroiditis, nodular regenerative chief cell hyperplasia
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How does nodular regenerative chief cell hyperplasia cause primary HYPOparathyroidism?
a few cells proliferate and try to save the PTG, but they are all eventually killed
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The vast majority of parathyroid chief cell neoplasms are _________, leading to _______; a primary clinical sign associated with this is _______.
functional; hypercalcemia; PU/PD
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Secondary C cell (thyroid gland) hyperplasia occurs secondarily to __________; there is an increase in _________ to try and combat _________.
functional PTH neoplasia; calcitonin; hypercalcemia
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Primary hyperparathyroidism is usually caused by a _________; clinical signs include.... (5)
tumor; PU/PD, weakness, generalized fibrous osteodystrophy (bone resorption), soft tissue mineralization, renal calculi
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Describe fibrous osteodystrophy.
increase in poorly mineralized bone in an attempt to stabilize bone that has been resorbed
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Non-functional chief cell adenomas are ________ and are common in __________.
subclinical; old rats
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Less common form of primary hyperparathyroidism that is usually functional and may require removal of multiple glands.
multifocal hyperplasia
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Diffuse hyperplasia of the parathyroid gland occurs secondarily to _________; some less common causes are... (3)
CKD; lack of dietary Ca2+, too much dietary Ph, or lack of dietary Vit D
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Secondary hyperparathyroidism to CKD occurs due to... (2)
lack of calcitriol and increased FGF-23.
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Secondary hyperparathyroidism in reptiles is caused by... (3)
CKD, lack of UV light, poor diet.
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Cancer-associated hypercalcemia can be caused by what kinds of cancer in animals? (4)
anal sac, lymphoma, stomach SCC (horses), SCC {all produce PTHrP}
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Describe humoral hypercalcemia of malignancy.
PTHrP has norma functions, but it is NOT usually secreted into circulation (except in cancer)
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Describe the synthesis and secretion of calcitonin.
produced and sits in cytoplasm; released in the event of hypercalcemia
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What clinical conditions are associated with excess or deficient calcitonin?
NONE
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Multiple endocrine neoplasia occurs due to __________.
a genetic defect
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Corrected calcium is __________; the best indicator of systemic status is ___________.
unreliable; iCa2+
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How do you collect a sample to measure iCa2+?
serum tube or heparinized tube; NOT EDTA- falsely decreases Ca2+
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What increases Ca2+?
PTH, PTHrP, Vit D
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Actions of PTH in the bone? (2)
increase Ca2+ resorption, increase Ph resorption
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Actions of PTH in the kidney? (3)
increased Ca2+ reabsorption, increased Ph excretion, activates Vit D by calcitriol
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Actions of PTH in the GI tract? (2)
increased Ca2+ absorption, increased Ph absorption
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Classic role of Vit D? Other roles? (3)
Classic: Ca-Ph homestasis; Other: immune system, RAAS, cardiovascular system
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What species cannot perform Vit D conversion in the skin?
dogs and cats
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Dietary Vit D of plant origin.
vit D2
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Dietary Vit D of animal origin.
Vit D3
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What decreases Ca2+? (1)
calcitonin
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Differentials for hypercalcemia.
- Hyperparathyroidism
- Addison's
- Renal Failure
- D Vit Excess
- Idiopathic
- Osteolytic
- Neoplastic
- Spurious/ systemic granulomatous dz
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Which differentials for hyperCa2+ have the higher Ca2+ values? (top 3)
- 1- neoplasia
- 2- primary hyperparathyroidism
- 3- Vit D toxicity
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Top 4 differentials for hyperCa2+ in dogs? (in order)
- 1- neoplasia
- 2- renal disease
- 3- hyperparathyroidism
- 4- addison's disease
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What are the 2 most common neoplasias causing hyperCa2+ in dogs?
lymphosarcoma, anal sac adenocarcinoma
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Top 3 differentials for hyperCa2+ in cats? (in order)
- 1- neoplasia
- 2- renal disease
- 3- urolithiasis
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What are the 2 most common neoplasias causing hyperCa2+ in cats?
lymphoma, squamous cell carcinoma
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Marked increase in Ca2+, marked decrease in phosphorous supports _____(2)_____.
primary hyperparathyroidism, neoplasia
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Increase, normal, or decrease in Ca2+, marked increase in phosphorous supports __________.
CKD
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Moderate increase in Ca2+ and phosphorous support __________.
vit D toxicity
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Mild increase in Ca2+ and phosphorous support __________.
Addison's disease
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Describe the txt of hyperCa2+. (4)
treat underlying cause, diuresis, corticosteroids, bisphosphonates
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Why is diuresis a part of txt for hyperCa2+?
causes Ca2+ excretion from kidneys
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How do bisphosphonates work?
decrease number and action of osteoclasts, decrease bone resorption
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Clinical signs of hypoCa2+? (6)
tremors/twitching, weakness, fasciculations, facial rubbing, seizures, anorexia
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Differential that causes the most profound hypoCa2+?
hypoparathyroidism
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Differentials for hypoCa2+? (8)
hypoparathyroidism, hypoalbuminemia, intestinal malabsorption, eclampsia/lactation; less common: acute pancreatitis, kidney disease, nutrition, ethylene glycol toxicity
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Emergency therapy for tetany?
calcium gluconate IV slowly until Ca2+ level is LOW NORMAL
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Cardiotoxicity caused by rapid IV Ca2+ infusion causes _________.
bradycardia
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If you suspect a hyperCa2+ disorder, what test should you order?
malignancy panel- PTH, iCa2+, PTHrP
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You can only interpret PTH in light of ________.
iCa2+
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Treatment for primary hyperparathyroidism.
surgical removal of parathyroid gland
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Post-op risks associated with parathyroidectomy?
risk for hypocalcemia- give Ca2+ and/or Vit D to maintain calcium in the low normal range
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Primary hyperparathyroidism is usually caused by a __________, causing...
single adenoma; excessive synthesis and secretion of PTH.
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Primary hyperparathyroidism usually occurs in dogs __________ [age].
middle-age to older (10yrs)
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Biochem changes that occur with primary hyperparathyroidism. (2)
hypercalcemia, hypophosphatemia
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UA changes with primary hyperparathyroidism.
USG<1.020, +/- crystalluria
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Why are hypercalcemic animals PU/PD?
Ca2+ interferes with ADH, causing nephrogenic DI
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Definitive diagnosis of primary hyperparathyroidism is achieved by...
paired PTH and iCa2+ measurements.
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Normally, if iCa2+ is high, PTH is _______.
low
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What is the prognosis for primary hyperparathyroidism?
excellent
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How do you diagnose idiopathic hyperCa2+?
rule out all other causes
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Idiopathic hyperCa2+ typically occurs in __________.
young to middle-aged cats
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With idiopathic hyperCa2+, Ca2+ is usually __________ increased.
mildly to moderately
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50% of cats with idiopathic hyperCa2+ will have __________ clinical signs.
no
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Treatment for idiopathic hyperCa2+. (3)
dietary modification, medical therapy with Prednisolone (promote calciuresis), bisphosphonates
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What are the nutritional goals when treating idiopathic hyperCa2+? (3)
lower Ca2+ diet, avoid excess vit D (salmon), increase water consumption
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3 causes of hypercalcemia with cancer.
humoral hyperCa2+ (mediated by PTHrP), cancer in BM (osteolysis), tumor metastasis to bone
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2 common causes of hematologic malignancy to BM.
lymphoma, multiple myeloma
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HyperCa2+ of malignancy is typically not from primary __________, such as __________.
bone tumors; osteosarcoma
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Clinical signs of hyperCa2+ of malignancy.
lethargy, anorexia, GI signs, PU/PD
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Hypoparathyroidism is usually due to ____________; it is most common in ____________.
immune-mediated destruction; young to middle-aged dogs (~4-5yrs)
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Clinical signs of hypoparathyroidism. (4)
[may wax and wane] muscle tremors, seizures, tetany, facial rubbing
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What biochem abnormalities may you find with primary hypoparathyroidism? (2)
hypocalcemia, hyperphosphatemia
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How do you definitively diagnose primary hypoparathyroidism?
paired PTH and iCa2+: hypoCa2+ and low or low normal PTH
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Acute treatment for primary hypoparathyroidism- hypocalcemic tetany? (2)
calcium gluconate IV slowly, monitor ECG for bradycardia/VPCs
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Long-term treatment of primary hypoparathyroidism? (2)
calcitriol (vit D), goal is to keep total Ca2+ low normal
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What is the prognosis for hypoparathyroidism with proper treatment?
excellent
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When and why does eclampsia occur?
first 3 weeks of lactation due to excessive calcium loss into milk without proper nutrition/supplementation
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Eclampsia most commonly affects _________ with __________.
small dogs; large litters
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What is the acute therapy for eclampsia? (2)
calcium gluconate IV slowly, monitor ECG for bradycardia/VCPs
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What is the long-term treatment of eclampsia?
calcium carbonate oral supplements until puppies are weaned
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Hyperparathyroidism can occur secondarily to... (2)
renal failure, nutritional
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Clinical signs of renal secondary hypoparathyroidism? (2)
PU/PD, GI signs (consistent with CKD)
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CBC and biochem abnormalities with secondary renal hypoparathyroidism? (4)
mild anemia of chronic disease, azotemia, hyperphosphatemia, high/N/low tCa2+
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UA findings associated with renal secondary hypoparathyroidism? (3)
isosthenuria, +/- proteinuria, +/- active sediment
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Treatment of renal secondary hypoparathyroidism. (6)
calcitriol, treat CKD: dietary and medical management- low Ph diet, GI protectants, SQ fluids, antihypertensive, manage proteinuria
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Nutritional secondary hyperparathyroidism results from... (3)
diet deficient in Ca2+, diet deficient in vit D, diet excessive in Ph
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Nutritional hyperparathyroidism causes __________; mineral is replaced by __________, a process called ____________.
skeletal Ca2+ depletion; fibrous connective tissue; fibrous osteodystrophy
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Clinical signs of nutritional secondary hyperparathyroidism. (4)
orthopedic disease- lameness, limb deformities in young animals; radiograph- decreased bone density, fractures
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How do you treat nutritional secondary hyperparathyroidism? (2)
confinement to reduce risk of fracture, complete and balanced diet (increase Ca:Ph ratio)
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What is the prognosis for nutritional hyperparathyroidism?
good, unless there are marked deformities
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