Relationships between thyroid hormone and catecholamines in experimental trauma.

The relationship between thyroid hormones (T4 and T3) and the catecholamines (adrenaline and noradrenaline) was studied as regards the possible value of administered T3 in the treatment of severely injured patients. Preparative surgery was performed on 36 pigs, 26 of which were then submitted to a standardized high-energy missile trauma to a hind leg. In 14 of the latter group, infusion of T3 was begun immediately before the trauma (n = 6), or after a delay of 8 h (n = 4) or 24 h (n = 4). A correlation was found between the disappearance rate of T3 and T4 and the catecholamine release, r = 0.79 (p less than 0.001) for adrenaline and 0.64 (p less than 0.01) for noradrenaline. T3 infusion started immediately before high-energy trauma resulted in raised serum levels of catecholamines, mainly noradrenaline, and was associated with a high mortality (4/6), and a clinical picture resembling thyrotoxic crisis. At 8 h the catecholamine-response to T3 administration was blunted and at 24 h post-trauma no influence on catecholamine levels could be determined. The high correlation between adrenaline release and disappearance rates of T3 and T4 after trauma suggests that adrenaline may in some way be connected to the fall in serum T3 and T4 concentrations following major trauma. The results further accord with the suggested role of T3 as a false neurotransmitter. Administration of T3 in the initial phase of the "low T3 state", presumably would not be of benefit for the severely injured patient.