18. Thyroid Flashcards
main raw material of thyroid hormone is ________ provided by the diet
inorganic iodide
inorganic iodide is extracted from the blood and converted to
organic iodine
iodine is incorporated into a tyrosine nucleus to form _________, and another is added to form _________
monoiodotyrosine, diiodotyrosine
two molecules of diiodotryosine combine to form
tetraiodthyronine (thyroxin/T4)
a monoiodotryosine combines with a diiodotryosine to form
triiodothyronine (T3)
TH is stored in the acini as _________, and reconstituted as needed
thryoglobulin
Over 90% of the TH in circulation under normal conditions is
T4
99% of T4 and T3 is bound to
proteins
most of T4 is bound to
thyroid binding globulin (TBG)
TBG is an
alpha-1 globulin
most T3 is bound to
TBG or albumin
unbound/free T4 and T3 are metabolically
active
free T4 is converted to T3, particularly in the
liver
80% of daily T3 is converted and utilized in the
liver
decreased T3/T4 cause hypothalamus to produce
TRH
increased T3/T4 inhibit both
TRH and TSH
High TSH, Low T3 and T4
primary hypothyroidism
failure of the thyroid gland is usually from
Hashimoto’s thyroiditis
TSH is low or absent from failure of pituitary to respond to TRH, or no TRH response to love T3/T4
secondary hypothyroidism
Low TSH, High T4/T3
hyperthryoidism
Graves disease, aka
diffuse toxic goiter
Graves disease is characterized by hyperthyroidism and of of the fallowing…
- goiter
- exopthalmous
- pretibial myxedema
circulating antibodies against the TSH receptors resulting in
continuous secretion of T3/T4
thyrotoxicosis factitia results from the ingestion of
TH
