Flashcards in Thyroid Deck (27):
What are the two major thyroid hormones?
How much T3 is produced in the thyroid itself?
Where does the majority of T3 come from
80% comes from peripheral breakdown of T4
How many half-lives do thyroid hormones have in steady state?
What does the thyroid do?
Regulates hormone production
This is done via the hypothalamic pituitary thyroid axis
How do we get thyroid hormone?
TSH secreted by anterior pituitary
T4 is converted to T3 outside the thyroid
What kind of disorder is primary hypothyroidism
Disorders of the thyroid gland
Aka: Hashimoto's thyroiditis
What kind of disorder is secondary hypothyroidism
Pituitary or hypothalamic dosorders
Sx of hypothyroidism
*When working a pt up for depression checking for hypothyroidism is ESSENTIAL*
Check TSH and a free T4 (or total but free is better)
Levels of hormones in subclinical hypothyroidism
Increased TSH but normal T4
Levels of hormones in hypothyroidism
Drug of choice for hypothyroidism
Long half life
Once daily dosing
IV dosing at 50% of oral dose
Dosing in mcg!
Little used hypothyroidism tx
Desiccated beef/pork thyroid gland (Armour -> mg dosing)*
*Obsolete and potential for allergy*
T3 and T4 mixtures (Liotrix) -> expensive, no real theraputic rationale
Dosed one daily in AM on EMPTY STOMACH
Typical dose = 100-112 mcg/day
Under what circumstances do we used alternative dosing of levothyroxine
Lower initial dosing for the elderly and pts w/ CV disease
Pregnancy usually requires higher dosing
Weight loss (cardinal sign)
Main cause of hyperthyroidism
Classic triad of Grave's disease
Opthalmopathy (bugged out eyes)
Dermopathy (pretibial myxedema)
Hormone levels in hyperthyroidism (dx)
Inhibits conversion of T4 to T3
Evaluate pts 3 months after D/Cing to check for recurrence
10xs more potent than PTU
Blocks oxidation of iodine in thyroid
No effect on T3 or T4
Dosing of methimazole for mild, moderate, severe, and maintenance is how many times per day