Endocrine Abstracts

Introduction: Many original research studies describes significant impact of thyroid hormones on muscle tissue. Hypo- and hyperthyroidism cause both functional and structural damage of muscles presented by many signs and symptoms of thyroid myopathy. Thus, it is interesting to compare the impact of thyroid dysfunction on hormones secreted by muscles – myokines.

Aim: The main goal of the project is to assess serum concentration of three myokines – irisin, titin and dystrophin and creatine kinase (CK) in patients with thyroid function impairment (overt hypo- and hyperthyroidisim) and in healthy control subjects.

Methods: The study enrolled 97 patients, newly diagnosed with overt thyroid dysfunction (48 with hypothyroidism and 49 with hyperthyroidism) and 40 healthy control subjects. Additionally, patients diagnosed with hypothyroidism were divided into two subgroups – long-lasting and short-term dysfunction. All subjects underwent routine clinical examination, laboratory tests (irisin, titin, dystrophin, thyroid-stimulating hormone - TSH, free thyroid hormones, anti-thyroid autoantibodies and CK concentrations), and thyroid ultrasound examination.

Results: The mean serum irisin level was lower in patients with long-lasting hypothyroidism than in other three groups (P<0.05). There was generally statistical difference in dystrophin levels between groups (P=0.035), with the highest dystrophin level in healthy controls and lowest in hyperthyroid patients, however post hoc analysis revealed the values at the border of statistical significance (P=0.076) between these groups. Similarly, the highest titin levels were presented by healthy controls, and the lowest by hyperthyroid patients (P=0.011) and group with long-lasting hypothyroidism (P=0.052). CK levels were statistically higher in long-lasting and short-term hypothyroidism than in hyperthyroid and control subjects (P<0.05).

Conclusions: Obtained results suggest that impact of thyrometabolic state varies among described myokins. This might be explained with multiply impact of hypo- and hyperthyroidism on muscle tissue, both dysfunction and destruction - demonstrated with high CK level.