Thyroid Medications

• Levothyroxine
  • 6 mcg/kg per day starting in you adults
    • Retest in 6 weeks
  • Decreased levothyroxine absorption
    • Bile acid binding agents
    • Iron, calcium, aluminum hydroxide
    • PPIs, sucralfate
  • Increased TBG concentration
    • Oral estrogen, tamoxifen, raloxifene
    • Heroin, methadone
  • Decreased TBG concentration (increases free thyroxine)
    • Androgens, glucocorticoids, Anabolic steroids
    • Slow-release nicotinic acid (niacin)
  • Increased Thyroid hormone Metabolism
    • Rifampin, Phenytoin, Carbamazepine
  • Effects
    • Subclinical: No effects with tx
    • Clinical hypothyroid: Weight loss, decrease lipids and bp
• Antithyroid Drugs
  • Methimazole
    • Teratogenic in first trimmest of pregnancy
    • Reassess with labs at 4-6 weeks after initiation, then every 2-3 months
      • Use total T3 and free T4 early on due to TSH possibly being suppressed for several months after initiation
    • SE: Agranulocytosis, rarely hepatotoxicity
      • Presents with fever, chills, sore throat within 90 days of starting
        • Get wBC w/differential
  • Propylthiouracil (PTU)
    • Reassess with labs at 4-6 weeks after initiation, then every 2-3 months
      • Use total T3 and free T4 early on due to TSH possibly being suppressed for several months after initiation
    • SE: Agranulocytosis, hepatotoxicity more common
      • Presents with fever, chills, sore throat within 90 days of starting
        • Get wBC w/differential
  • Radioactive Iodine (RAI)
    • When the above cannot be tolerated, want to avoid surgery, and those unlikely to achieve remission ono the above alone
    • Residual hypothyroidism possible in Graves’ disease
      • May exacerbate ophthalmopathy (exophthalmos, periorbital edema, vision changes)
      • Prednisone given when moderate to severe prior to surgery
      • Mild lid lag does not need prednisone