Thyroid Flashcards
what is the main raw material of thyroid hormone
how do we get this raw material
what happens next
inorganic iodide
provided by the diet
extracted from the blood and converted to organic iodine
iodide ingested and taken into the blood is converted to
- -> ___ + ___
- -> ____ + ____
- -> ____
iodine which binds to tyrosine
which forms monoiodtyrosine which binds with iodine
which forms diiodotyrosine
what forms T4
diiodotyrosine + diiodotyrosine = tetra/thyroxin
what is another name for T4
thyroxin
tetraiodothyronine
what forms T3
monoiodotyrosine + diiodotyrosine
what is another name for T3
triiodothyronine
what is thyroid hormone stored in? as what ?
acini
thyroglobulin
most of thyroid hormone in circulation is what type
T4 90%
99% of T4 and T3 are bound to what in the blood
protein
most of T4 is bound to what
most of T3 is bound to what
TBG (thyroid binding globulin)
TBG and albumin
thyroid binding globulin is what type of protein
alpha 1 globulin
1% of T4 and T3 is found where
FREE or unbounded
metabolically active in cells
free T4 is converted to
where
T3
in the liver cells for utilization
what percent of daily T3 is converted and utilized by the liver
80%
80% of __ is converted and utilized by the liver
T3
decreased levels of T3 and T4 cause what to happen
TRH production in hypothalamus
increased levels of T3 and T4 cause what to happen
inhibit TSH and TRH
TSH high, T3 and T4 are low indicate what
primary hypothyroidism
hashimotos
TSH is normal or low
T3 and T4 are low
indicates what
secondary hypothyroidism
why is TSH normal or low in secondary hypothyroidism
pituitary doest respond to TRH or low T3/T4 doesnt trigger TRH response
TSH is low and
T3 and T4 are high indicates what
hyperthyroidism
is T3 or T4 more elevated in hyperthyroidism
T3
what causes hyperthyroidism
due to autonomous hyperfunction or thyroid stimulators in the blood
what is graves disease
hyperthyroidism
what is another name for graves disease
diffuse toxic goiter
what are the requirements to have graves disease
hyperthyroidism and one of the following:
goiter
exophthalmous
pretibial myxedema
what causes graves disease
due to circulating antobodies against TSH receptors which causes continuous secretion of T3/T4
what is the most common cause of hyperthyroidism
graves disease
what results from the ingestion of thyroid hormone
thyrotoxicosis factitia
calcitonin is made by what cells of the thyroid gland
C cells of thyroid
what does calcitonin do
reduce Ca in the blood
decrease absorption in GI
decrease osteoclasts
decrease Ca and phosphate reabsorption in the kidney
parathyroid hormone is secreted by what
parathyroid glands found inside the thyroid gland
what does PTH do
increase Ca in the blood
increase absorption in GI
increase osteoclasts
increase Ca and phosphate reabsorption in the kidney
what is the 5th most abundant element in the body
Calcium
calcium is the __ most abundant element in the body
5th
adults have calcium content of what
1kg
2% of body weight
all but __% of calcium is found in the bone
where is this % found
1%
intra and extracellular space
in blood, all calcium is found in the
plasma
what percent of calcium is free
what is this also called
50%
ionized calcium
what percent of calcium is bound to protein
40%
80% - albumin
20% - globulins
what percent of calcium exists as anions
examples
10%
bicarbonate
lactate
citrate
what is normal serum calcium levels
8.5 to 10.5 mg
what form of calcium is the only form that is regulated by calciotropic hormones
free or ionized calcium
decisions of total serum calcium concentration should not be made without considering what
albumin
plasma proteins
total serum calcium is easier or harder to measure than ionized/free calcium
easier
..but make sure to consider the protein concentrations to determine the difference bound to protein and free/ionized
in patients with multiple myeloma, the ___ concentration is often increased, which leads to excessive binding of Ca to ____ which may elevate total serum calcium concentration, yet the ___ level may be normal
globulin
monoclonal paraprotein
ionized calcium
when is ionized free calcium considered useful to diagnose a patient
multiple myeloma
serum calcium levels above what usually cause symptoms
critical levels =
medical emergency =
11.5 mg
12mg
15mg (severe hypercalcemia)
hypercalcemia results from what
increased mobilization of calcium from bones or increased intestinal absorption
primary hyperparathyroidism or bone metastasis from breast, prostate, thyroid, lung
what are the symptoms of hypercalcemia
ACUTE confusion
fatigue
lethargy
> 13 mg
what are the symptoms of chronic hyperparathyroidism
stones - kidney moans - abdominal pain groans - myalgia bones - bone pain psychiatric overtones
PTH and PTHrP levels are normal indicates what
rule out PT adenoma
suggest malignancy, hypervitaminosis A or D, milk alkali syndrome, granulomatous disease, meds, lithium, thiazides
hypocalcemia results from what
absent or impaired parathyroid glands
OR
impaired vitamin D synthesis
what causes primary hypothyroidism
failure of thyroid gland - hashimotos thyroiditis - MC
iodine deficiency
enzymatic defects
