Pathophysiology of the Parathyroid Glands

Question 1

what cells secrete calcitonin?

Answer 1

parafollicular cells (C cells) in thyroid gland

Question 2

calcitonin acts to ____________ calcium concentration

Answer 2

decrease

Question 3

what hormone does calcitonin oppose?

Answer 3

parathyroid hormone

Question 4

what are the general effects of parathyroid hormone?

Answer 4

increase calcium
decrease phosphorous

Question 5

what hormone is the major regulator of calcium?

Answer 5

parathyroid hormone

Question 6

who are parathyroid/Kursteiner’s cysts common in?

Answer 6

dogs
incidental finding

Question 7

how common is primary hypoparathyroidism?

Answer 7

uncommon

Question 8

what are the etiologies of primary hypoparathyroidism?

Answer 8

lymphocytic parathyroiditis
bilateral thyroidectomy
metastatic neoplasia
sepsis
idiopathic

Question 9

what cytokines inhibit parathyroid hormone secretion?

Answer 9

IL-1
IL-6

Question 10

is there a breed disposition to primary hypoparathyroidism?

Answer 10

no apparent

Question 11

what are the clinical signs of primary hypoparathyroidism due to?

Answer 11

low extracellular (blood) calcium concentration

Question 12

why does lack of calcium have neuromuscular effects?

Answer 12

calcium makes nerves less permeable to sodium
calcium is needed for release of acetylcholine

Question 13

what are the laboratory findings for primary hypoparathyroidism?

Answer 13

low to undetectable iPTH
decreased total calcium and iCa: hypocalcemia
increased phosphorous: hyperphosphatemia

Question 14

what is primary hyperparathyroidism caused by?

Answer 14

parathyroid tumor

Question 15

what is the most common cause of primary hyperparathyroidism in dogs, cats, and horses?

Answer 15

parathyroid (chief cell) adenoma

Question 16

what laboratory findings are associated with primary hyperparathyroidism?

Answer 16

within normal limits or increased iPTH
increased calcium and iCa
low to lower-end of RI phosphorous

Question 17

true/false: the mass is usually not palpable with primary hyperparathyroidism

Answer 17

true

Question 18

what do primary hyperparathyroidism patients get in the urinary tract?

Answer 18

calcium-containing uroliths: 30%
secondary urinary tract infections: 24%

Question 19

when can we see nephrocalcinosis with primary hyperparathyroidism?

Answer 19

Ca>16 mg/dL

Question 20

when can skeletal changes be seen with primary hyperparathyroidism?

Answer 20

chronic cases

Question 21

what skeletal changes can be seen with chronic cases of primary hyperparathyroidism?

Answer 21

diffuse skeletal demineralization
pathologic fractures
changes can be most notable in skull

Question 22

what is secondary hyperparathyroidism commonly due to?

Answer 22

dietary problem

Question 23

what dietary problems can lead to secondary hyperparathyroidism?

Answer 23

improper calcium:phosphorous ratio in diet
low vitamin D

Question 24

who is secondary hyperparathyroidism most common in?

Answer 24

growing animals or exotic species

Question 25

what are the laboratory findings with secondary hyperparathyroidism?

Answer 25

low-end of reference interval to decreased total calcium and iCa low, within normal, or occasionally high phosphorous increased iPTH

Question 26

what are the clinical signs of secondary hyperparathyroidism usually due to?

Answer 26

hypocalcemia

Question 27

what skeletal changes can chronic secondary hyperparathyroidism lead to?

Answer 27

pain on movement limb deformities generalized skeletal demineralization and fibrous oseodystrophy thinning of long bone cortices

Question 28

what is reptile metabolic bone disease due to?

Answer 28

secondary hyperparathyroidism

Question 29

what is seen in reptile metabolic bone disease?

Answer 29

pathologic fractures swelling of long bones decalcification and shortening/bowing of mandible soft, deformed shells of eggs

Question 30

what animals are at a higher risk for reptile metabolic bone disease?

Answer 30

insectivores may need fortified food herbivores with limited exposure to UV light should get vitamin D3 supplementation

Question 31

which animals are not at increased risk of reptile metabolic bone disease?

Answer 31

those housed outside reptiles that eat whole mammalian prey

Question 32

who is more likely to have secondary hyperparathyroidism due to renal?

Answer 32

adult mammals

Question 33

what is secondary hyperthyroidism due to renal triggered by?

Answer 33

decreased calcium and rising serum phosphorous

Question 34

GFR determines filtration of _____________ and ____________

Answer 34

calcium phosphorous

Question 35

what are calcium levels like in dogs with chronic renal failure?

Answer 35

10% have low total Ca 40% have low ionized Ca

Question 36

what are the clinical signs in renal secondary hyperparathyroidism due to?

Answer 36

renal failure

Question 37

what clinical signs are associated with renal secondary hyperparathyroidism?

Answer 37

vomiting, dehydration, PU/PD mild hypocalcemia

Question 38

what happens to the parathyroid glands in chronic renal failure?

Answer 38

hypertrophy

Question 39

how often do we see skeletal changes with renal secondary hyperparathyroidism?

Answer 39

occasionally

Question 40

what is the most common cause of persistent hypercalcemia in dogs?

Answer 40

humoral hypercalcemia of malignancy

Question 41

what tumors have the highest incidence of humoral hypercalcemia of malignancy?

Answer 41

lymphoma apocrine gland anal sac adenocarcinoma multiple myeloma squamous cell carcinoma

Question 42

what does humoral hypercalcemia of malignancy produce?

Answer 42

parathyroid hormone related protein

Question 43

what are the laboratory findings associated with humoral hypercalcemia of malignancy?

Answer 43

increased calcium and iCa low to within normal phosphorous decreased iPTH increased PTHrp

Question 44

what are the causes of reptile metabolic bone disease?

Answer 44

diet problems lack of exposure to UVA and UVB cool temperatures

Question 45

what hormones regulate calcium homeostasis?

Answer 45

parathyroid hormone calcitriol/active vitamin D calcitonin parathyroid hormone-related peptide fibroblast growth factor-23

Question 46

what inhibits parathyroid hormone secretion through the Ca-sensing receptor?

Answer 46

high calcium high calcitriol

Question 47

what does cacitriol binding to a receptor that modulates DNA expression do?

Answer 47

control expression for calcium absorption and transport in the gastrointestinal tract increases calcium, phosphorous, and magnesium absorption inhibits parathyroid hormone secretion

Question 48

do skeletal changes occur with primary hypoparathyroidism?

Answer 48

no

Question 49

what are the clinical signs of primary hyperparathyroidism?

Answer 49

usually mild pu/pd anorexia/GI signs generalized muscle weakness occasional, mild CNS signs

Question 50

low phosphorous in primary hyperparathyroidism makes mineralization _______________

Answer 50

less likely

Question 51

what is the ideal ratio of Calcium:Phosphorous in a diet?

Answer 51

2:1 bad: low calcium, excess phosphorous

Question 52

what are the neuromuscular signs associated with nutritional secondary hyperparathyroidism?

Answer 52

nervous, ataxic, weak rub muzzle, eyes, ears intermittent muscle tremors generalized tetany convulsive seizures

Question 53

what triggers renal secondary hyperparathyroidism?

Answer 53

decreased GFR and rising serum phosphorous hyperphosphatemia

Question 54

what happens in the kidneys that contributes to secondary hyperparathyroidism?

Answer 54

decreased filtration: increased phosphorous decreased absorption: decreased calcium decreased activation of vitamin D: decreased calcium

Question 55

does the hypocalcemia in renal secondary hyperparathyroidism cause clinical signs?

Answer 55

not usually

Question 56

what skeletal changes might you see with renal secondary hyperparathyroidism?

Answer 56

demineralization fibrous osteodystrophy