[Recent results concerning muscular disorders arising from thyroid gland dysfunction (author's transl)].

The right number of muscular disorders which may be observed clinically in thyroid dysfunction contrast with the paucity of knowledge concerning the mechanisms of action of the thyroid hormones. Those which have been described allowed the following conclusions to be made: 1) The thyroid hormones simultaneously increase the oxydative phosphorylation in mitochondria and the activation of glycogen phosphorylase. 2) They modify the properties of cell membrane without noticiably changing the cytoplasm (light and electron microscopically). These modifications are concommitant with a reduction in resting membrane potential associated with anomalies of Na+ conductance and Ca+ uptake. 3) The appearance and the number of motor units in each muscle is dependant on the hormonal impregnation. However, these diverses actions do not reveal wether the thyroid hormone receptors are in the muscle or if they act via the intermediary of a neuronal trophic factor.