Endocrine Abstracts

Introduction: Severe thyroid disorders are usually associated with myopathy. Muscle weakness may occur in both hypothyroidism and hyperthyroidism. However, only hypothyroid patients experience increase in creatine kinase levels, depicting destruction of muscle fibers. There were recently some reports showing the lowering in serum concentrations of large sarcomere proteins – titin (TTN) and dystrophin (DMD) in patients with hypo- and hyperthyroidism.

Aim: The aim of the study is to preliminarily evaluate the changes in serum levels of TTN and DMD in patients with severe thyroid disorders and after restoration of euthyroidism.

Methods: The study enrolled 21 patients, newly diagnosed with overt thyroid dysfunction (11 with hypothyroidism and 10 with hyperthyroidism) and 12 healthy control subjects. All subjects underwent laboratory tests (TTN, DMD and thyrometabolic state) at baseline and patients were reevaluated after restoration of euthyroidism.

Results: The median serum TNT and DMD levels were lower in patients affected by thyroid disorders than in control group (P<0.05). After restoration of euthyroidism hypothyroid patients showed increase in DMD levels (P=0.0009), with no difference compering to controls (P=0.1768), while their TTN levels remain low (P=0.2787). In hyperthyroid patients there were no statistically significant changes in DMD and TTN concentrations (P>0.05), that were still lower comparing with controls (P=0.02817; 0.0049, respectively).

Conclusions: Obtained results suggest that even after restoration of biochemical and clinical euthyroidism, these disorders might still negatively affect muscle tissue metabolism. That might be reflected by decreased levels of large sarcomere proteins. However, this preliminary study needs following evaluations on larger groups to confirm this promising results.