Thyroid Flashcards
Hypothyrodism in dogs
- Goal of therapy
- Drugs
Replace hormone the body is not producing
Liothyronine (T3) or Levothyroxine (T4)
Levothroxine pharmacokinetics
Requires less frequent dosing and has lower risk of causing throtoxicois (excessive T4 levels)
Dosed in mg/kg - Reduced risk of over supplementation in large patient by doings mg/m2
Must be given for the rest of patient’s life
How to monitor hypothyroidism in dogs
Monitor by measuring T4 levels
Start measuring 4 weeks after starting therapy
Be mindful of drugs that could interfere with thyroid test results (phenobarbital, zonisamide, sulfonamides, glucocrticoids, phenylbutazone, quinidine)
Only veterinary approved product for hypothyroidism in dogs
Thyro-tabs
Goal of therapy for cats with hyperthyroidism
Stop excessive hormone production
Therapy options for hyperthyroidism in cats
Surgery (thyroidectomy) = remove abnormal tissue
Radioactive iodine = remove abnormal tissue
Diet with Hill’s y/d = prevent production (iodine uptake)
Pharmacologic therapies = prevent production (interfere with synthesis), prevent release of performed hormone, prevent conversion of T4 to T3
Pharmacologic options for Hyperthyroidism in cats
Methimazole
Propylthiouracil
Iodides/Iodinated Contrast Agents
Methimazole
Inhibits thyroid synthesis
Consistently efficacious
Side effects uncommon and most are manageable
Propylthiouracil
Inhibit thyroid synthesis
Inhibit conversion of T4 to T3 in tissues
Higher incidence of serious side effects (higher risk)
Iodides/Iodinated Contrast Agents
Efficacy is variable and often transient
Inhibit thyroid synthesis
Inhibit released of performed hormone
Inhibit T3 to T4 conversion in periphery
3 Methimazole drugs
Tapazole (human approved)
Felimazole (veterinary approved)
Transdermal methimazole (no commercial product, obtained through compounder)
Side effects of Methimazoles
Mild/common = GI signs (vomiting), transient hematologic changes on CBC Severe/uncommon = refractory GI signs, idiosyncratic reactions (facial excoriation, hepatopathy, bone marrow suppression)
Carbimazole
Converted in the body to methimazole
