Thyroid Drugs - Kruse Flashcards
Levothyroxine
T4
Liothyronine
T3
Liotrix
4:1 T4:T3
4 antithyroid agents
Radioactive iodine sodium
Methimazole
Potassium iodide
Propylthiouracil [PTU]
Levothyroxine - use
Hypothyroidism (thyroid hormone replacement), myxedema
Levothyroxine, Liothyronine - toxicities
Tachycardia, heat intolerance, tremors, arrhythmias
Liothyronine - use
Short-term suppression of TSH
Propylthiouracil, Methimazole - MoA
What else does PTU do?
Inhibits thyroid hormone synthesis - Inhibits thyroid peroxidase, blocking oxidation of iodide. Also inhibits coupling of DIT and MIT to form T3 and T4.
PTU - also blocks 5’-deiodinase, inhibiting peripheral conversion of T4 to T3
A patient is given PTU. What is different on labs afterwards than if he was given Methimazole?
PTU = significant decrease in T3 concentration compared to T4
PTU, Methimazole - most common toxicity
Most serious toxicity?
Maculopapular pruritic rash (+ systemic signs)
Agranulocytosis (rare)
Methimazole - unique toxicity
Aplasia cutis (TERATOGEN)
Perchlorate (ClO4-), Pertechnetate (TcO4-), Thiocyanate (SCN-) – MoA
Inhibit iodide uptake via competitive inhibition
A patient tries to OD on her anion inhibitor thyroid medications. How to fix?
Give lots of iodide
Grave’s disease, young, small/mild disease…treatment?
If pregnant?
Methimazole
PTU if pregnant
Grave’s disease, very large gland and severe disease…treatment?
Thyroidectomy
Grave’s disease, over 21 y/o…treatment?
Side effect?
Radioactive iodide
Hypothyroidism (requires hormone replacement)
Grave’s disease, being treated w/ Methimazole or PTU. Still struggling w/ tachycardia, HTN, A. fib. Additional treatment?
Non-sympathomimetic beta-blocker (Metoprolol, Propranolol, Atenolol)
Grave’s disease, being treated w/ Methimazole or PTU. Still struggling w/ tachycardia, HTN, A. fib. Also has Asthma/COPD. Additional treatment?
Why?
Diltiazem (Ca-channel blocker)
Asthma/COPD = contraindication for beta blocker
Patient has hyperthyroidism and acutely starts experiencing fever, tachycardia, HTN, diarrhea, and neuro abnormalities. Diagnosis?
Treatment?
Thyroid storm
Tx = Beta blockers + Potassium iodide + PTU/methimazole + IV hydrocortisone