parathyroid Flashcards
where is 99% is bone in the body?
in bone
where is the smallest store of calcium in the body?
extracellular
what pool is calcium is the regulated pool?
extracellular calcium
where is Ca2+ absorbed?
the gut
is Ca2+ excreted?
yes by the kidney
how many total parathyroid glands are in most animals?
4 glands (2pairs)
what is the main organ of Ca2+ and phosphate metabolism?
parathyroid
what are the active cells of the parathyroid?
chief cells
what type of hormone is PTH?
peptide hormone
what are the inactive cells of the PT?
oxyphil cells
what cells synthesize PTH?
chief cells of the PT
in the human PTH half life is 7-10 days, how long is it in the dog?
10-15 min
what terminus of PTH is the biologically active part?
the N-terminus
what stimulates PTH?
low serum calcium
PTH counters the actions of what?
calcitonin
PTH had direct or indirect effects on bone metabolism of Ca2+?
direct
PTH had direct or indirect effects on kidney metabolism of Ca2+?
direct
PTH had direct or indirect effects on GI metabolism of Ca2+?
indirect
is the response to PTH rapid or slow?
rapid
where does the calcium come from in the bone?
hydroxyapatite
what is PTH’s effect on the kidney?
- increased absorption of calcium by distal tubles
- formation of calcitriol
- excretion of phosphate in the urine
what is PTH’s effect on the small intestine?
increased absorption of calcium and phosphate
-(consequence of calcitriol from kidney)
increased blood calcium and calcitriol in the blood does what to blood phosphorus?
reduces phosphorus in blood via renal excretion
what cells produce calcitonin?
parafollicular (C-cells) of the thyroid gland
what is the roll of calcitonin?
decrease Ca2+ in the ECF
- moves Ca2+ to bone by blocking osteoclast activity
- inhibits Ca++ absorption by intestines
- inhibits renal tubular cell reabsorption of Ca++
what shuts off PTH activity?
increased Ca++ in blood
what is hypophosphatemia, caused by calcitonin?
- moves phosphate from ECF to bone
- inhibites phosphate absorption by renal tubules
what is calcitriol?
the bioactive from of vitamin D
what is the role of calcitriol?
increases CA++ and phosphorus in the blood
what results from disturbances of serum levels of Ca++ (increased serum Ca++)?
hyperparathyroidism
what are the effects of hyperparathyroidism metabolism on bone?
- increased bone resoprtion
- decreased radiographic density (radiopacity)
- incomplete fractures
what are the signs of hyperparathyroidism?
- depressed mentation
- muscular weakness
- peptic ulcers
- lethargy
- renal failure
what is calcitonin’s effect of blood phosphorus?
decreases it
what is PTH’s effect of blood phosphorus?
decreases it
which type of hyperparathyroidism is more common?
secondary
which form of hyperparathyroidism is an adenoma of chief cells?
primary
effects of primary hyperparathyroidism on urine/blood Ca++/phosphorus:
- hypercalciuria, hypercalcemia
- hyperphosphaturia, hyophosphatemia
what type of hyperparathyroidism is caused by chronic renal failure?
secondary
what does renal damage do to calcitriol?
reduces calcitriol synthesis
as [phosphorus] increases, what happens to [Ca++]?
[Ca++] decreases
secondary hyperparathyroidism do to blood/urine calcium?
normocalcemia and hypocalciuria
secondary hyperparathyroidism do to blood/urine phosphorus?
hyperphosphatemia
what causes rubber jaw disease?
secondary hyperparathyroidism
what type of hyperparathyroidism is causes by nutritional deficiencies and mineral imbalance?
secondary
what diets can cause secondary hyperparathyroidism?
low Ca++ and high phosphorus
what are two causes of hypoparathyroidism?
- lymphocytic parathydroiditis
- surgery for hyperthyroidism
what are the symptoms of hypoparathyroidism?
- hyperflexia
- larygneal spasm
- convultions
what is the treatment for acute hypoparathyroidism?
IV calcium gluconate
what is the treatment for chronic hypoparathyroidism?
oral calcium carbonate and vit. D
low phosphorus diet
where are the sites of synthesis for erythropoietin (EPO)?
- kidney (primary; peritubular cells)
- liver (not in dog)
what controls the negative feedback of erythropoietin synthesis/
-hypoxia
what site does EPO act on?
red bone marrow
what are the actions of erythropoietin?
- increases differentiation of hemocytoblasts into reticulocytes STEM CELL ACTION
- increases synthesis of key proteins
- alpha and beta globins
- transferrin receptor
