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44 Cards in this Set

  • Front
  • Back
Primary hypothyroidism?
malfunction of the thyroid itself
not enough TSH from pituitary
not enough TRH from hypothal
most severe form of hypothyroidism?
myxedema (accumulation of MPS and water in dermis --> puffy skin)
What is the most common cause of hypothyroidism in US?
Hashimoto's thyroiditis
AB atttack thyroglobulin, thyroperoxidase, or TSH receptor
What is thyroglobulin?
contains activated tyrosine molecules that get joined by enzymes to make MIT and DIT
How is iodine taken up?
it accumulates in thyroid
transports by energy dependent process up a gradient using a Na-I Symporter (this last step can be regulated by drugs)
What happens to I once it is taken up?
oxidized by H2O2 and TPO
Enzyme joins activated iodine atoms to activated tyrosines of thyroglobulin --> MIT and DIT
TPO couples MIT and DIt --> T3 and DIT x2 --> T4
What can inhibit TRH
Somatostatin (SST)
Waht things in diet can --> Hashimoto's thyroiditis?
Lack of I2 in diet, remedied with iodized salt
Sphiach can interfere with thyroid hormone production
What do goitrogens do? Examples?
block T2/T4 release
cabage can do this
What other conditions are associated with severe iodide deficiency?
congenital hypothyroidism
What chemicals may induce hypothyroidism?
aminosalicylic acid
What happens with amiodorone metabolism?
elevates serum i levels
They rise enough to inhibit thyroid hormone production
Inhibits T4 --> T3 conversion
Metabolites block binding of T2 to receptors
What effect does pregnancy have on thyroid function?
--> increased TBG during pregnancy --> hypothyroid state that resolves after birth
Treatments of hypothyroidism?
synthetic thyroxine (levothyroxine/L-T4)
Liothyronine T3
Does levothyroxine or liothyronine have longer half-life?
levothyroxine (7 d)
Does levothyroxine or liothyronine have more adverse effects?
liothyronine (cardiotoxicity)
Effects of T3/T4 overdose?
signs of hyperthyroidism
increased Ca loss --> increased risk for osteoporosis
How is hypothyroidism treated in pregnancy?
levothroxine is given (it is identical to natural T4)
Dose might have to be increaed
Which is the most common cause of hyperthyroidism?
Graves' disease
AB that cross-react with human TSH receptors
What causes the exopthalmos seen in hyperthyroidism?
autoAB activation of TSH-R on orbital fibroblasts --> hyaluronic acid production --
> increased osmotic load of tissues --> passive swelling
What is the 2nd most common cause of hyperthyroidism?
toxic nodular goiter (no exopthalmos)
What happens in thyroid adenoma, clinically?
cancerous cells in thyroid gland that overproduce thyroid hormones
Amiodarone and hyperthyroidism?
structurally similar to T4, plus it has high I content
Can cause hypothyroidism when serum I levels are too high and suppress TSH secretion
Cause hyperthyrodism when it brings I levels up to a more normal level
4 types of drugs used to treat hyperthyroism?
drugs taht modify production of thyroid hormone
drugs that block I uptake
drugs that modify tissue response
drugs that destroy the thyroid gland
Basic mechanims of thioamides
Drugs in this category?
modify the production ofo thyroid hormone
They bind TPO competitively and inhibit I incorporation and coupling

What is the main difference between PTU and the other thioamides?
Inhibits 5 deiodinase and therefore reduces T4 --> T3 conversion
Which thioamide has the longest half life?
Methimazole (given once a day, 6-8 hr half life)
Which thioamide is good in pregnancy?
PTU (more strongly bound to proteins)
Thioamide can penetrate the placental barrier
Adverse effects of thioamides?
agranulocytosis can occur rarely
basic mechanism of anion inhibitors?
block I uptake
Which are the anion inhibitors
how do anion inhibitors work?
they compete withe I for NIS
can displace I alrady taken up by cell
what is major use of anion inhibitors?
adverse effects?
to block I uptake in amiodarone induced hyperthyrodism
Which is the preferred hyperthyroidism treatment for pts over 21 yo?
what may be required if pt is elderly?
pretreatment wiht methimazole
what results from radioidide?
wht lifelong levothyroxine replacement possibly needed
Actions of I
inhibition of thyroperoxidase, colloid resorption, proteolysis
hyperthyroid sx subside in 1-2 dyas, and 10-14 d for peak effect
cons of I?
leaves thyroid loaded with I which is problematic for I and thioamide tx to follwo
when is I given?
reduces size and vascularity of thyroid before thyroidectomy (given as KI)
thyrotoxic crisis when hormone production must be stopped immediately
adverse efects of I
sore throat
ulcers of mucous membranes
metallic taste
can cause fetal goiter
What can block T4-->T3?
iodinate contrasting aents
What is guanethidine?
norE blocking agen used in eye to ameliorate exopthalmos
Thyroid storm?
thyrotoxic crisis caused by hyperthyroidism wiht a precipitating factor (infectioin, etc)
--> sudden exacerbation of all sx of thyrotoxicosis (life threatening)
treatment of thyroid storm?
Beta blockers to control CV probs and block T4-->T3
PTU to block synth of new hormone and T4-->T3
KI to block proteolysis of TG
Dexamethasone to protect against shock and prevent T4-->T3
Iodinated contrast to block T4-->T3
supportive therapy
what should be avoided in thyroid storm?
can increase free T4 and T3