Endocrine Pharmacology II - Thyroid Hormones

  1. Thyroid agents
  2. Thyrotropin RH -> Thyroid SH -> T3 + T4
  3. Dopamine and somatostatin inhibit TSH
  4. Levothyroxine (T4) and Liothyronine (T3) are used to treat hypothyroidism
  5. Thioamides, Iodide, and Beta Blockers treat hyperthyroidism
  6. Low thyroid hormone most commonly caused by Iodine deficiency
  7. Hashimoto's thyroiditis is most common cause of hypothyroidism in US
  8. Low thyroid hormone -> manifests as thick lips, large tongue, malocclusion, impacted mandibular molars
  9. T3 = Triiodothyronine, T4 = Thyroxine
  10. Levothyroxine is DOC for low thyroid -> long half-life (7 days), converted to T3 intracellularly
  11. Can cause bone maturation, nervousness, heat intolerance
  12. Inhibited absorption by soy, bran, and coffee
  13. Liothyronine is synthetic T3 - more potent than levothyroxine, but only preferred for short term TSH suppression
  14. Liotrix (combination T3 and T4) and dessicated thyroid sometimes used
  15. Myxedema is a type of hypothyroidism that often coincides with coronary artery disease
  16. Amiodarone can induce hypothyroidism from rT3 production
  17. Hyperthyroidism is more common in women than men
  18. Hyperthyroidism can cause facial osteoporosis, BMS, accelerated dental eruption
  19. Thioamides include methimazole and propylthiouracil (PTU), and inhibit a peroxidase reaction that converts Iodine to TH
  20. Methimazole 10x more potent than PTU, but PTU also inhibits peripheral deiodination of T3 and T4
  21. Nausea, GI distress, and altered taste or smell occur as side effects for thioamides
  22. Anion inhibitors - perchlorate, pertechnetate, and thiocyanate block Iodide uptake
  23. I-131 treats thyrotoxicosis by destroying thyroid parenchyma, contraindicated in pregnant women as it can pass through the placental barriers
  24. Iodides (potassium Iodide and Lugol's solution) were commonly used prior to thioamides, and are contraindicated in pregnancy
  25. Hyperthyroidism increases sensitivty to Warfarin, decreases sensitivity to cardiac glycosides
  26. PTU is safe in first trimester, but otherwise both thioamides are contraindicated in pregnancy
  27. Beta blockers control cardiovascular issues in thyrotoxicosis
  28. Graves' Disease - antibodies against TSH receptor sites