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Titin and dystrophin serum concentrations changes in patients affected by thyroid disorders.

OBJECTIVE
It is well established, that thyroid hormones significantly affect skeletal muscles function, causing symptoms like myalgia and muscle weakness. Hypothyroid patients present increased levels of creatine kinase (CK), indicating muscle destruction. Lately, we proposed new serum markers of muscle disturbances in thyroid disorders - titin (TTN) and dystrophin (DMD). The aim of this study is to determine the association between thyroid status, muscle metabolism and serum levels of TTN and DMD in patients affected by hypo- and hyperthyroidism, before and after the treatment.


DESIGN AND PATIENTS
In the study 56 subjects were enrolled. The studied group consisted of 16 patients with newly diagnosed overt hypothyroidism and 20 patients with hyperthyroidism. 20 healthy controls were also included in the study. Body composition, thyroid hormones and biochemical markers of muscle deterioration levels were evaluated before and after restoration of euthyroidism.


RESULTS
DMD and TTN levels were noticeably lower in the hypothyroid group and hyperthyroid group in comparison with controls, at the border of statistical significance. Along with the thyroid hormones and CK normalization, DMD levels increased in hypothyroid group, with no significant lowering of TTN levels. However, TTN concentrations and fT3/fT4 ratio became significantly lower than in controls. Hyperthyroid patients experienced no significant changes in TTN and DMD.


CONCLUSIONS
Presented data indicates, TTN and DMD might be the potential new markers of musculoskeletal deterioration in thyroid disorders. In addition, the shift in TTN and DMD serum concentrations after the treatment of hypothyroidism accompanied by decreased fT3/fT4 ratio may suggest the influence of chosen therapeutic approach on muscle metabolism.