Single-Dose T3 Administration

Abstract

A single dose of liothyronine has both short-term and long-term effects. There is clearly a different lag time between the serum concentrations of triiodothyronine and its effects on the heart and pituitary, respectively. The increase in serum triiodothyronine concentration occurred within hours and was then followed by an increase in HR. The increased HR was transient and was followed by a reduction in TSH concentration. The suppression of TSH was delayed but was more sustained. Thus, sustained TSH reduction beyond 24 hours was achieved by a single dose of liothyronine that produced only brief increases in serum triiodothyronine levels and transient increases in HR.