Chapter 58: Thyroid Gland Flashcards
The thyroid gland is made up of cells arranged how?
in circular follicles
what is the function of follicular
stores and released thyroid hormone
what is parafollicular cells also known as
thyrocalcitonin
when is thyrocalcitonin released
it is released when serum calcium levels are high, they are an antagonist to PTH
what are the two hormones that the thyroid gland produces
triiodothyronine (T3) and thyroxine (T4)
which hormone is released in a greater amount?
T4
most of the released T4 will undergo conversion to T3 by what?
peripheral tissue enzymes
how much T3 is converted from T4
80%
which hormone is more potent
T3
the thyroid function test (TSH) is the most sensitive test for what
screening and diagnosing hypothyroidism
what does the thyroid function test (TSH) differentiate bwetween?
differentiates between first degree and secondary diseases
what does the serum T3 test diagnose
hyperthyroidsm
what is the level for a serum T3 test?
230-620 pg/dL
what is a primary form of thyroid hormone deficiency
Hashimoto’s thyroiditis (autoimmune)
what lab results would indicate a thyroid hormone deficiency?
elevated TSH and a decreased T3/T4 levels
what are some clinical manifestations related to hypothyroidism?
peri-orbital edema, intolerance to coldness, brittle hair and nails, extremely low heart rate and body temperature, fatigue, lethargy, impaired mention, weight gain (despite no increases in caloric intake)
what is the prototype of T4 synthetic agent
levothyroxine
how can levothyroxine be administered
PO and IV
true or false: short-term treatment is require in most thyroid disorders
FALSE; long term treatment is usually required.
true or false: pharmacotherapy agents provide symptomatic relief and is NOT a cure.
true.
we should educate our patients that it could take how long to begin seeing therapeutic effects from these drugs?
4-6 weeks
what half-life do thyroid drugs have?
seven days
thyroid medications stimulate the CV system which leads to what? so you should take what precautions?
increases cardiac response to catecholamines, limits the intake of caffeine-containing beverages, uses other sympathomimetic agents cautiously.
what levels should we monitor on patients taking thyroid medications and why?
lipid and glucose levels, these drugs could cause dyslipiedmia and hyperglycemia.
should you take thyroid medications with food or on an empty stomach?
take on an empty stomach in the morning. 30-60 minutes before breakfast.
why do you take thyroid medications on an empty stomach?
food can significantly decrease the absorption of the drug
how do you monitor the effectiveness of thyroid drugs?
clinical picture and lab tests
too much thyroid medications can lead to what
a hyperthyroid state
how often should you monitor drug effectiveness?
every 6-8 weeks initially and when changing doses.
why do you monitor drug effectiveness every 6-8 weeks initially?
TSH levels are slow to normalize.
what is the drug interaction between levothyroxine and warfarin?
levothyroxine speeds up the destruction of vitamin-K dependent clotting factors, so you would need to reduce the dose of warfarin because its effects are enhanced.
how would you adjust the dose of digoxin when combining with levothyroxine?
increase dose when converting hypothyroid state to a euthyroid state
what is a primary form of hyperthyroidism?
Graves’ disease (most common)
what are the lab results you would see with hyperthyroidism?
decreased TSH levels and increased T3 and T4
what are some clinical manifestations of hyperthyroidism?
tachycardia/dysrhythmias, forceful cardiac contractions/angina, nervousness and insomnia, intolerance to heat, skin is warm and moist, increase in appetite but weight loss.
graves disease can cause what to the eyes?
exophthalmos
what is exophthalmos?
immune mediated infiltration of the EOMs and orbital fat
how can you treat exophthalmos?
high dose glucocorticoids and/or surgery
what are the drug treatments of hyperthyroidism?
radioactive iodine, thionamides, non radioactive iodine solutions (Lugol’s), beta-adrenergic blockers (used to treat symptoms like elevated blood pressure and tachycardia)
what is the goal of treating hyperthyroidism?
euthyroid state
too much drugs to treat hyperthyroidism can induce what
hypothyroid state
methimazole inhibits what two things?
inhibits the synthesis of thyroid hormones, inhibits the conversion of T4 to T3 in the tissues.
what effect does methimazole have on stores of thyroid hormone
no effect
how long does it take methimazole to induce a euthyroid state
3-12 weeks
what is the major ADR of methimazole?
agranulocytosis (risk of infection)
what are the early signs of agranulocytosis
sore throat and fever
how does agranulocytosis develop
it develops rapidly, but may not see CBC changes quickly.
what is the major ADR of propylthiouracil?
sudden onset of hepatotoxicity and rash
what are the four differences between propylthiouracil and methimazole?
can cause severe liver injury, short half life (2-3 daily doses), crosses placenta less readily (given to pregnant women in 1st trimester), has an effect on existing stores of thyroid hormone.
what is propylthiouracil most effective in treating?
thyrotoxic crisis
what class is sodium iodide-131
radioactive iodine solutions
where does sodium iodide-131 concentrate in and where does it get destroyed?
concentrated in the thyroid gland and is radioactivity destroyed in the thyroid tissue
what is the goal of sodium iodide-131?
only partially destroy the gland so the amount of TH produced and secreted is low
what is sodium iodide-131 also used for?
a diagnostic test to identify the extent of thyroid activity
how do the dose of sodium iodide-131 differ when being used for thyroid cancer?
doses are larger due to exposing the person to higher amounts of radioactivity.
what is the nonradioactive iodine?
lugol’s solution
what is lugol’s solution used for?
used to suppress thyroid function 10 days before surgery
lugol’s solution reduced iodine to what
iodide in the GI tract before being absorbed.
in high concentrations, iodide has paradoxical suppressant effects on the thyroid by what 3 mechanisms?
reducing iodine uptake by the thyroid, inhibiting TH synthesis, and inhibiting the release of TH into the blood
chronic ingestion of lugol’s solution produce?
iodism
what are the clinical manifestations of iodism
brassy taste in mouth, burning sensation in the mouth/throat, sore gums, nasal congestion, increased salivation.
iodine is corrosive and overdose could cause what?
GI tract injury
what are signs and symptoms of GI tract injury?
abdominal pain, nausea and vomiting, and diarrhea.
what is a complication of GI injury due to iodine OD?
swelling of the glottis–>asphyxiation
what is treatment for GI injury due to OD on iodine?
gastric lavage and giving Na thiosulfate.
