Pathophysiology of the Parathyroid Glands Flashcards
what cells secrete calcitonin?
parafollicular cells (C cells) in thyroid gland
calcitonin acts to ____________ calcium concentration
decrease
what hormone does calcitonin oppose?
parathyroid hormone
what are the general effects of parathyroid hormone?
increase calcium
decrease phosphorous
what hormone is the major regulator of calcium?
parathyroid hormone
who are parathyroid/Kursteiner’s cysts common in?
dogs
incidental finding
how common is primary hypoparathyroidism?
uncommon
what are the etiologies of primary hypoparathyroidism?
lymphocytic parathyroiditis
bilateral thyroidectomy
metastatic neoplasia
sepsis
idiopathic
what cytokines inhibit parathyroid hormone secretion?
IL-1
IL-6
is there a breed disposition to primary hypoparathyroidism?
no apparent
what are the clinical signs of primary hypoparathyroidism due to?
low extracellular (blood) calcium concentration
why does lack of calcium have neuromuscular effects?
calcium makes nerves less permeable to sodium
calcium is needed for release of acetylcholine
what are the laboratory findings for primary hypoparathyroidism?
low to undetectable iPTH
decreased total calcium and iCa: hypocalcemia
increased phosphorous: hyperphosphatemia
what is primary hyperparathyroidism caused by?
parathyroid tumor
what is the most common cause of primary hyperparathyroidism in dogs, cats, and horses?
parathyroid (chief cell) adenoma
what laboratory findings are associated with primary hyperparathyroidism?
within normal limits or increased iPTH
increased calcium and iCa
low to lower-end of RI phosphorous
true/false: the mass is usually not palpable with primary hyperparathyroidism
true
what do primary hyperparathyroidism patients get in the urinary tract?
calcium-containing uroliths: 30%
secondary urinary tract infections: 24%
when can we see nephrocalcinosis with primary hyperparathyroidism?
Ca>16 mg/dL
when can skeletal changes be seen with primary hyperparathyroidism?
chronic cases
what skeletal changes can be seen with chronic cases of primary hyperparathyroidism?
diffuse skeletal demineralization
pathologic fractures
changes can be most notable in skull
what is secondary hyperparathyroidism commonly due to?
dietary problem
what dietary problems can lead to secondary hyperparathyroidism?
improper calcium:phosphorous ratio in diet
low vitamin D
who is secondary hyperparathyroidism most common in?
growing animals or exotic species
what are the laboratory findings with secondary hyperparathyroidism?
low-end of reference interval to decreased total calcium and iCa
low, within normal, or occasionally high phosphorous
increased iPTH
what are the clinical signs of secondary hyperparathyroidism usually due to?
hypocalcemia
what skeletal changes can chronic secondary hyperparathyroidism lead to?
pain on movement
limb deformities
generalized skeletal demineralization and fibrous oseodystrophy
thinning of long bone cortices
what is reptile metabolic bone disease due to?
secondary hyperparathyroidism
what is seen in reptile metabolic bone disease?
pathologic fractures
swelling of long bones
decalcification and shortening/bowing of mandible
soft, deformed shells of eggs
what animals are at a higher risk for reptile metabolic bone disease?
insectivores may need fortified food
herbivores with limited exposure to UV light should get vitamin D3 supplementation
which animals are not at increased risk of reptile metabolic bone disease?
those housed outside
reptiles that eat whole mammalian prey
who is more likely to have secondary hyperparathyroidism due to renal?
adult mammals
what is secondary hyperthyroidism due to renal triggered by?
decreased calcium and rising serum phosphorous
GFR determines filtration of _____________ and ____________
calcium
phosphorous
what are calcium levels like in dogs with chronic renal failure?
10% have low total Ca
40% have low ionized Ca
what are the clinical signs in renal secondary hyperparathyroidism due to?
renal failure
what clinical signs are associated with renal secondary hyperparathyroidism?
vomiting, dehydration, PU/PD
mild hypocalcemia
what happens to the parathyroid glands in chronic renal failure?
hypertrophy
how often do we see skeletal changes with renal secondary hyperparathyroidism?
occasionally
what is the most common cause of persistent hypercalcemia in dogs?
humoral hypercalcemia of malignancy
what tumors have the highest incidence of humoral hypercalcemia of malignancy?
lymphoma
apocrine gland anal sac adenocarcinoma
multiple myeloma
squamous cell carcinoma
what does humoral hypercalcemia of malignancy produce?
parathyroid hormone related protein
what are the laboratory findings associated with humoral hypercalcemia of malignancy?
increased calcium and iCa
low to within normal phosphorous
decreased iPTH
increased PTHrp
what are the causes of reptile metabolic bone disease?
diet problems
lack of exposure to UVA and UVB
cool temperatures
what hormones regulate calcium homeostasis?
parathyroid hormone
calcitriol/active vitamin D
calcitonin
parathyroid hormone-related peptide
fibroblast growth factor-23
what inhibits parathyroid hormone secretion through the Ca-sensing receptor?
high calcium
high calcitriol
what does cacitriol binding to a receptor that modulates DNA expression do?
control expression for calcium absorption and transport in the gastrointestinal tract
increases calcium, phosphorous, and magnesium absorption
inhibits parathyroid hormone secretion
do skeletal changes occur with primary hypoparathyroidism?
no
what are the clinical signs of primary hyperparathyroidism?
usually mild
pu/pd
anorexia/GI signs
generalized muscle weakness
occasional, mild CNS signs
low phosphorous in primary hyperparathyroidism makes mineralization _______________
less likely
what is the ideal ratio of Calcium:Phosphorous in a diet?
2:1
bad: low calcium, excess phosphorous
what are the neuromuscular signs associated with nutritional secondary hyperparathyroidism?
nervous, ataxic, weak
rub muzzle, eyes, ears
intermittent muscle tremors
generalized tetany
convulsive seizures
what triggers renal secondary hyperparathyroidism?
decreased GFR and rising serum phosphorous
hyperphosphatemia
what happens in the kidneys that contributes to secondary hyperparathyroidism?
decreased filtration: increased phosphorous
decreased absorption: decreased calcium
decreased activation of vitamin D: decreased calcium
does the hypocalcemia in renal secondary hyperparathyroidism cause clinical signs?
not usually
what skeletal changes might you see with renal secondary hyperparathyroidism?
demineralization
fibrous osteodystrophy