[Stimulation of peripheral conversion of thyroxine to triiodothyronine by ovine somatotropic hormone in the eel (Anguilla anguilla L.)].

One injection of ovine growth hormone (1.27 X 10(-5) USP units/g body weight) determines in the Eel, 1 day later, a twofold decrease in plasma thyroxine level as well as a twofold increase in plasma triiodothyronine level. These modifications of circulating iodothyronine levels result from a considerable stimulation of the peripheral deiodination of thyroxine to triiodothyronine, shown by a kinetic study of labelled thyroxine metabolism. The increase of production of metabolically active hormone, triiodothyronine, induced by growth hormone could represent the (or one of the) mechanism(s) implicated in the synergic action of these two hormones on Vertebrate growth.