Indications for Intravenous T3 and T4

Area of Science:

• Endocrinology
• Pharmacology

Background:

• Thyroid hormone therapy is typically oral substitution for hypothyroidism.
• Intravenous (IV) thyroid hormone use is limited to specific clinical scenarios.

Purpose of the Study:

• To review indications and outcomes of intravenous thyroid hormone therapy.
• To evaluate the efficacy of IV thyroid hormones in various critical conditions.

Main Methods:

• Review of existing literature on intravenous thyroid hormone administration.
• Analysis of studies involving IV levothyroxine and liothyronine in different patient populations.

Main Results:

• IV thyroid hormones are used for malabsorption, unconsciousness, sedation, and shock.
• Studies in preterm infants and post-cardiac surgery patients showed normalized T3 levels and improved ventilation/cardiac index, but no mortality benefit.
• IV levothyroxine is standard for myxoedema coma, with potential cardiac benefits in brain-dead organ donors.

Conclusions:

• Intravenous thyroid hormone therapy has specific, limited indications.
• Efficacy is demonstrated for certain parameters, but broad mortality or morbidity benefits are not established.
• Oral therapy is often equivalent, and IV use is temporary until oral intake is possible.