Endocrine Abstracts

Objective: Myostatin may negatively regulate skeletal muscle mass. Serum myostatin levels have positive associations with obesity and insulin resistance. Thyroid dysfunction may affect body weight, energy expenditure, and glucose metabolism. We evaluated the serum myostatin levels in different thyroid function statuses.

Subjects and methods: We recruited 30 newly-diagnosed hyperthyroid (HY) patients and treated them with anti-thyroid regimens as clinically indicated. Thirty euthyroid (EU) patients were recruited as controls. We measured laboratory parameters at the baseline and at 6 months, and calculated their changes. Associations between the levels of myostatin and free thyroxine (fT4), thyroid-stimulating hormone (TSH), or log transformation of TSH (logTSH) were analyzed.

Results: There were no significant difference of myostatin levels among the HY and the EU patients, both at baseline (median [Q1, Q3]: 16.25 [11.42, 20.23] vs 17.50 [11.80, 21.56] ng/ml, P = 0.599) and at 6 months (median [Q1, Q3]: 27.27 [19.11, 32.66] vs 23.20 [16.02, 29.43] ng/ml, P = 0.306). Serum myostatin levels had no associations with levels of fT4, TSH, or logTSH, both at baseline or 6 months. However, changes of myostatin had positive associations with changes of logTSH (β = 2.323, P = 0.019). The association between changes of myostain levels and changes of logTSH remained significant after adjustment for sex and age (β = 2.505, P = 0.015).

Conclusions: Serum myostatin levels of the HY patients were not different with that of the EU patients. In this study, changes of serum myostatin levels had positive associations with changes of logTSH. The real impact of thyroid function statuses on myostatin levels remained to be investigated.