[Non-thyroid indications of treatment with thyroid hormones]

The use of thyroid hormone is currently strictly limited to thyroid diseases. Several recent papers have examined the effects of thyroid hormone in non-thyroidal diseases. These studies examined either the use of the pharmacological properties of thyroid hormone or the effect of the correction of the decrease in triiodothyronine (T3) associated with non-thyroid illnesses.

Intravenous administration of T3 improves the cardiac index during ongoing cardiac surgery, with a paradoxical decrease in the incidence of atrial fibrillation. T3 administered by the oral route also improves the cardiac index in the medium term in dilated cardiomyopathy. No benefit on survival has been demonstrated in non-thyroidal diseases when using the pharmacological properties of thyroid hormone. Other situations, such as transplantation or neural rescue after cardiac arrest, are currently under study. In non-thyroidal diseases, administration of thyroxine (T4) has no effect because of the deeply disturbed metabolism of thyroid hormones.

Adverse metabolic effects of T4 and T3 therapy have probably been overestimated and may depend on the dose and on the time of administration in the course of the disease. Indications in cardiac surgery and cardiac diseases need to be clarified. To further understand the value of thyroid hormones in non-thyroidal diseases, placebo-controlled studies using small doses of T3 are required.