Hypothyroid Flashcards
Most common causes of primary hypothyroidism
Hashimotos, Iatrogenic (drugs, surgery, radiation),
other–> endemic, iodine deficiency, congenital
Drugs that cause HYPOthyroidism
amiodarone subitinib lithium interferon thalidomide bexarotene ethionamide rifampicin anti-thyroid meds (PTU, methimazole)
Complications of Hypothyroidism
Subclinical–> hight TSH, normal thyroid hormone
Myxedema–> swelling&edema in legs and face
Myxedema Coma–> progressive weakness, turpor, low body temp, hypoventilation, hypoglycemia, water toxicity, shock, death
Lab findings with HYPOthyroidism
elevated TSH
decreased free thyroxine
Lab findings in Hashimoto’s
will see elevated TSH, decreased free thyroxine as well as
antithyroglobulin antibody (ATgA)
Antimicrosomal antibody (AMA)
increased cholesterol, LDH AST, ALT, CPK
Tx guidelines for Hyppthyroidism
TX with Synthetic L-thyroxine (1st line)
if TSH>10 mIU/L
plus signs and symptoms
Natural Thyroid Hormone
Desiccated Thyroid
contains (38mcg of levothyroxin, 9mcg liothyronine, 65mg of thyroid
Levothyroxine in tx of Hypothyroidism
first line med–> synthetic thyroidhormone (L-thyroxine) T4
Absorption of Levothyroxine
40-80% depending on what the pt is eating (increases with fasting, decreases with fiber)
Distribution of Levothyroxine
99% is protein bound
Metabolism of Levothyroxine
80% hepatic (as an active metabolite)
Excretion of Levothyroxine
80% renal (de-iodenization), 20% fecal
half life=6-7 days
Things that can decrease absorption of Levothyroxine
cholestyramine calcium carbonate sucralfate alumiun hydroxide ferrous sulfate soybean formula dietary fiber suplements food
Things that can increase elimination of levothyroxine (decrease serum levels of it)
carbamazepine phenytoin rifampin sertraline quetiapine phenobarbitol
Levothyroxine Administration
Oral–>taken on empty stomach; 30 mins prior to breakfast 4 hrs after dinner
IV==> less than or equal to or 50% of oral dose as IV dose
feeding tube–> make suspension–>give–>wait 1 hr to restart feed.
if pt on intermittent feeding, want to wait as long as possible before giving med again
