Levothyroxine

Summary

Levothyroxine, often called by its brand name Synthroid, is a medication used to increase thyroid hormone levels. It’s used to treat hypothyroidism and should be taken by patients on an empty stomach first thing in the morning. If the dose is too high, Levothyroxine can cause hyperthyroidism which may manifest as a variety of symptoms including insomnia, tachycardia or palpitations, and weight loss.

Key Points

• Levothyroxine (Synthroid)
  • Mechanism
    • Synthetic version of the thyroid hormone thyroxine (T4)
    • Dose will be adjusted based on regularly scheduled blood work
  • Clinical Uses
    • Hypothyroidism
      • Myxedema coma
      • Hashimoto’s Disease (chronic lymphocytic thyroiditis)
      • Simple goiter
      • Usually is a life-long therapy
      • May take up to a month before effects are seen
  • Side Effects and Adverse Reactions
    • Drug/food interactions
      • Best taken first thing in the morning on an empty stomach, before food and other medications
      • Antacids, soy, dietary fiber, calcium, and iron can impair the absorption of levothyroxine
    • Hyperthyroidism
      • Tachycardia, palpitations
      • Weight loss
      • Insomnia
      • Anxiety
      • Diaphoresis
      • Amenorrhea
    • Abdominal effects
      • Nausea/vomiting, Abdominal cramping, Diarrhea, Anorexia
    • Decreased bone density