Hypothyroidism Treatment

Levothyroxine

• 1st-line agent for treatment of hypothyroidism
• May be used to manage myxedema coma
• Safe for use in pregnancy
• Actions:
  • Used as a replacement therapy in hypothyroidism to substitute thyroid hormone
  • Long half-life (T_½), slow onset, regular bioconversion which is appropriately regulated by the tissues to the biologically active compound T₃

• Effects: Safe and predictable effects
  • Requires several weeks to achieve peak therapeutic effects with regular oral dosing

• Due to different bioavailability of the various preparations of Levothyroxine, patients are encouraged to use the same brand of Levothyroxine
  • If a change in brand is needed, the patient’s serum TSH should be retested every 6 weeks and dosage of Levothyroxine be re-titrated

Liothyronine

• Actions:
  • Short T_½, rapid onset
  • Biologically active compound (no conversion is necessary)
  • Used as a replacement therapy in hypothyroidism to substitute thyroid hormone

• Generally not recommended for routine treatment of hypothyroidism due to its rapid onset and turnover which requires more frequent administration and increases the risk of hyperthyroidism
• Useful in management of myxedema coma (when its rapid onset and short duration of action are required)
• Effects: Require 3 days to achieve peak therapeutic effects