parathyroid glands Flashcards
which pharyngeal pouches make the parathyroid gland ?
3rd and 4th pharyngeal pouch
where are the receptors of the PTH ?
bone and kidney
what cells make the PTH ?
chief cells
what is the net effect of PTH ?
increased calcium levels in plasma
lowers phosphate levels in the plasma , by increasing the excreted levels of it in the urine
what are the different triggers for the secretion of the parathyroid hormone ?
low levels of calcium
high levels of phosphate
low levels of vitamin D
what is the effect of magnesium on the parathyroid gland ?
high magnesium means less PTH secreted ( like calcium)
what is the effect of very low levels of magnesium on the PTH release ?
super low magnesium levels inhibits the release of the PTH
hypocalcemia is often seen with severe hypomagnesemia
what is the effect of low calcium and low magnesium on the ecg ?
prolonged QT interval
what is the effect of PTH on the kidney ?
increased calcium absorption
decreased phosphate absorption
increased vitamin d production
what is the effect of PH on the GI tract ?
increased calcium and phophate absoption
what is the effect of PTH on bones ?
it binds to the osteoblasts which then expresses RANk-L on their surface
which binds to RANK receptor on osteoclasts which breaks down bones and hence increase serum calcium
what is the blood supply of the parathyroid ?
superior and inferior thyroid arteries
how does PTH affect the levels of vitamin D ?
PTH upregulates the expression of 1 alpha hydroxylase in the kidneys to form the more active form of vitamin D
how can the activation of vitamin D happen independently ?
in cases of sarcoidosis
what is the difference in the effect of bones with different doses of PTH ?
continous administration leads to bone resorption
low dose once daily leads - bolus administration leads to an increase on bone mass
what are the different cells found in bones and what are their functions ?
osteoblasts - make the bone , have parathyroid hormone receptors
osteoclasts bykasar
how do the osteoblasts and osteoclasts work together ?
the osteoblasts secrete M-CSF , which stimulates the osteoclasts
osteoblasts have an RANK-L receptor which also binds to osteoclasts to activate it
what is PTHrP ?
hormone produced in large amounts in tumors
leads to hypercalcemia
what are the three forms of hyperparathyroidism ?
primary - overactive gland
secondary - hypocalcemia
tertiary - renal failure
what are the common causes of primry hyperPTH ?
parathyroid adenoma
what are the associated serum findings in primary hyperPTH ?
hypercalcemia
phosphaturia
high or normal calcium levels in the urine
what is the classic presentation of primary hyperPTH ?
Stones ,bones, groans , psychiatric overtones
what is the specific bone disease associated with 1ry hyperPTH ?
osteitis fibrosa cystica
associated with brown tumors
where exactly is the pathology in association with osteitis fibrosa cystica ?
subperiosteal bone resorption
what does groans refer to in 1ry hyperPTH ?
constipation recurrent gastric ulcers
what is the treatent for 1ry hyperPTH and what are the associated complications ?
treatment: parathyroidectomy
risk of recurrent laryngeal nerve damage
post op hypocalcemia
what is the presentation of post parathyroidectomy hypo calcemia ?
numbness or tingling in the fingers, toes and hands
twitching or cramping of facial muscles
what is the cause of tertiary hyperPTH ?
secondary hyperPTH w tawel awy
bas hena VERY hig PTH
high PTH and high calcium like with primary
what is the pathology in terms of renal failure in calcium phosphate ?
increased phosphate , decreased vitamin D levels
decreased calcium from the gyt , decreased calcium from the plasma
causing hypocalcemia
increase in PTH
what is familial hypocalciuric hypercalcemia ?
autosomal dominant disorder
abnormal calcium sensing - due to abnormal CaSR receptors
what are the levels of of phosphate in the urine in hyperPTH ?
increased phosphate levels
increased cAMP
what are the calcium levels in FHH ?
high serum calcium
normal PTH
low level of calcium in the urine
what is the key finding associated with FHH ?
low urinary calcium
what are the calcium levels in hypopituitarism ?
low PTH secretion
low calcium levels
what are the signs and symptoms of hypocalcemia ?
neuromuscular irritability - tingling and spams
tetany
seizures
what are the specific signs seen in hypocalcemia ?
trousseau’s sign - hand spams with BP cuff inflation
chvosteks sign - facial contraction on nerve tapping
what are the common causes of hypoparathyroidism ?
surgical excision after thyroid surgery
hemochromatosis
wilsons disease
metastatic cancer
what is autoimmune polyendocrine syndrome type 1 ?
autosomal recessive disorder
mutation of the AIRE gene
what is the triad associated with APS-1?
mucocutaneoux candidiasis
autoimmune hypoparathyroidism
addison’s disease
what is digeorge syndrome ?
failure of the 3rd and 4th pharyngeal pouches
the triad :
loss of thymus
loss of parathyroid
congenital heart defect
what is the treatment for hypoparathyroidism ?
calcium and calcitrol
recombnant human PTh
what is pseudohypoparathyroidism ?
group of disorders
kidney and bone unresponsive to PTH
abnormal PTH receptor function
what are the calcium and PTH levels in pseudohypoPTH ?
high PTH levels and low calcium levels
what is albrights hereditary osteodystrophy ?
form of pseudohypoparathyroidism
autosomal dominant
hypocalcemia and hyperphosphatemia
what are the clinical features associated with AHO ?
short stature
shortened fourth and fifth metacarpals
rounded facies
mild mental retardation
this is a form of pseudohypoparathyroidism
why is there an increase in vitamin D levels in sarcoidosis ?
due to the independant activation of vitamin d where histiocytes activate the 1 alpha hydroxlase enzyme
what are the PTH levels in sarcoidosis ?
PTH is suppressed due to the increased levels of calcium
we have hypercalcemia due to the increased production of vitamin D
which cancers are associated with the release of PTHrp ?
squamous cell carcinoma of the lung and renal cell carcinoma
what is the classic scenario associated witha patient who has pagets disease ?
a man over the age of 50 who’s hat doesn’t fit him anymore with tinnitus
due to narrowing of the acoustic foramen
what is the effect seen upon administration of exogenous calcium ?
as expected :
the serum calsium will increase
the PTH levels will decrease
an increase in vitamin D
what is the classic scenario associated with milk alkali syndrome ?
hypercalcemia and metabolic alkalosis ( high bicarb)
associated with a patient taking too many antacids for GERD
what are the expected serum calcium and PTH levels in a patient after space travel ?
decreased bone density
decreased calcium levels
decreases PTH
decreased urinary cAMP
what are the features of osteporosis ?
all the levels are normal
7ata el calcium
but decreased osteoblast activity
increased osteoclast activity
and increased RANK L activity
what type of patient is at a higher risk of low magnesium levels ?
alcoholics
