The authors report a pertinent documented with subsidiary examination uncommon case of sensitive-motor polineuropathy, in the: course of hyperthyroidism, looking like be coherent to give it the name of "thyrotoxic polineuropathy". In despite of few scientific works on this subject, strong arguments are presented intending to link the process of hyperthyroidism and the progressive degeneration, distal, symmetric and simultaneous, of peripheric nerves. Final considerations show the difficulty of recognizing the etiopathogeny of the degenerative process of peripheral nerves remembering the possibility of toxic, carencial or auto-immune nature.