[Comparison between spontaneous changes in circulating triiodothyronine (T3 and reverse-T3) and those induced by acute intravenous administration of thyroliberin]. / Confronto tra le variazioni spontanee delle triiodotironine circolanti (T3 e rT3) e quelle indotte da carico endovenoso acuto di tiroliberina (TRH).

ABSTRACT

Some of the Authors had previously observed a slight-non significant decrease in T3 serum levels 10 minutes after TRH intravenous administration. On the other hand, it is now well known that reverse T3 (rT3) inhibits T4 conversion to T3. We therefore investigated the changes in T3 and rT3 serum levels within the first ten minutes of a 200 micrograms TRH test in a group of 10 healthy women in fertile age. No significant change in T3 was demonstrated. On the other hand, rT3 showed a significant-yet slight-decrease 6 minutes after TRH injection (from 0,27 to 0,21 ng/ml, p less than 0,05). Some feasible explanations for this phenomenon are given in the text.